CVE-2026-27820

zlib is a Ruby interface for the zlib compression/decompression library. Versions 3.0.0 and below, 3.1.0, 3.1.1, 3.2.0 and 3.2.1 contain a buffer overflow vulnerability in the Zlib::GzipReader. The zstream_buffer_ungets function prepends caller-provided bytes ahead of previously produced output but fails to guarantee the backing Ruby string has enough capacity before the memmove shifts the existing data. This can lead to memory corruption when the buffer length exceeds capacity. This issue has been fixed in versions 3.0.1, 3.1.2 and 3.2.3.

zlib is a Ruby interface for the zlib compression/decompression library. Versions 3.0.0 and below, 3.1.0, 3.1.1, 3.2.0 and 3.2.1 contain a buffer overflow vulnerability in the Zlib::GzipReader. The zstream_buffer_ungets function prepends caller-provided bytes ahead of previously produced output but fails to guarantee the backing Ruby string has enough capacity before the memmove shifts the existing data. This can lead to memory corruption when the buffer length exceeds capacity. This issue has been fixed in versions 3.0.1, 3.1.2 and 3.2.3.

Details

A buffer overflow vulnerability exists in Zlib::GzipReader.

The zstream_buffer_ungets function prepends caller-provided bytes ahead of previously produced output but fails to guarantee the backing Ruby string has enough capacity before the memmove shifts the existing data. This can lead to memory corruption when the buffer length exceeds capacity.

Recommended action

We recommend to update the zlib gem to version 3.2.3 or later. In order to ensure compatibility with bundled version in older Ruby series, you may update as follows instead:

• For Ruby 3.2 users: Update to zlib 3.0.1
• For Ruby 3.3 users: Update to zlib 3.1.2

You can use gem update zlib to update it. If you are using bundler, please add gem "zlib", ">= 3.2.3" to your Gemfile.

Affected versions

zlib gem 3.2.2 or lower

Credits

calysteon

References

• https://hackerone.com/reports/3467067

Ruby is a fast and easy interpreted scripting language for object-oriented programming. It has many functions for processing text Files and perform system management tasks (such as Perl).

Security Fix(es):

The attack vector is a potential Denial of Service (DoS). The vulnerability is caused by an insufficient check on the length of a decompressed domain name within a DNS packet.

An attacker can craft a malicious DNS packet containing a highly compressed domain name. When the resolv library parses such a packet, the name decompression process consumes a large amount of CPU resources, as the library does not limit the resulting length of the name.

This resource consumption can cause the application thread to become unresponsive, resulting in a Denial of Service condition.(CVE-2025-24294)

zlib is a Ruby interface for the zlib compression/decompression library. Versions 3.0.0 and below, 3.1.0, 3.1.1, 3.2.0 and 3.2.1 contain a buffer overflow vulnerability in the Zlib::GzipReader. The zstream_buffer_ungets function prepends caller-provided bytes ahead of previously produced output but fails to guarantee the backing Ruby string has enough capacity before the memmove shifts the existing data. This can lead to memory corruption when the buffer length exceeds capacity. This issue has been fixed in versions 3.0.1, 3.1.2 and 3.2.3.(CVE-2026-27820)

Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to 0.6.5 and 0.5.15, several Net::IMAP commands accept a "raw data" argument that is sent verbatim after validation to prevent command injection. However, if a server does not support non-synchronizing literals, it may still be possible to inject arbitrary IMAP commands inside non-synchronizing literals. A server without support for non-synchronizing literals may interpret the "+}\r\n" as the end of a malformed command line and respond with a tagged BAD. In that case, the contents of the literal will be interpreted as one or more new pipelined commands, allowing a CRLF command injection attack to succeed. This affects criteria for #search and #uid_search; search_keys for #sort, #thread, #uid_sort, and #uid_thread; and attr for #fetch and #uid_fetch. This vulnerability is fixed in 0.6.5 and 0.5.15.(CVE-2026-47240)

Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to 0.6.5 and 0.5.15, several Net::IMAP commands accept a raw string argument which is only validated to prevent CRLF injection and then sent verbatim. If this string is derived from user-controlled input, an attacker can force the next command to be absorbed as a continuation of the first command. This will cause the first command to eventually fail, but also prevents it from returning until another command is sent (from another thread). That other command will not return until the connection is closed. This vulnerability is fixed in 0.6.5 and 0.5.15.(CVE-2026-47241)

Ruby is a fast and easy interpreted scripting language for object-oriented programming. It has many functions for processing text Files and perform system management tasks (such as Perl).

Security Fix(es):

The attack vector is a potential Denial of Service (DoS). The vulnerability is caused by an insufficient check on the length of a decompressed domain name within a DNS packet.

An attacker can craft a malicious DNS packet containing a highly compressed domain name. When the resolv library parses such a packet, the name decompression process consumes a large amount of CPU resources, as the library does not limit the resulting length of the name.

This resource consumption can cause the application thread to become unresponsive, resulting in a Denial of Service condition.(CVE-2025-24294)

zlib is a Ruby interface for the zlib compression/decompression library. Versions 3.0.0 and below, 3.1.0, 3.1.1, 3.2.0 and 3.2.1 contain a buffer overflow vulnerability in the Zlib::GzipReader. The zstream_buffer_ungets function prepends caller-provided bytes ahead of previously produced output but fails to guarantee the backing Ruby string has enough capacity before the memmove shifts the existing data. This can lead to memory corruption when the buffer length exceeds capacity. This issue has been fixed in versions 3.0.1, 3.1.2 and 3.2.3.(CVE-2026-27820)

Ruby is a fast and easy interpreted scripting language for object-oriented programming. It has many functions for processing text Files and perform system management tasks (such as Perl).

Security Fix(es):

The attack vector is a potential Denial of Service (DoS). The vulnerability is caused by an insufficient check on the length of a decompressed domain name within a DNS packet.

An attacker can craft a malicious DNS packet containing a highly compressed domain name. When the resolv library parses such a packet, the name decompression process consumes a large amount of CPU resources, as the library does not limit the resulting length of the name.

This resource consumption can cause the application thread to become unresponsive, resulting in a Denial of Service condition.(CVE-2025-24294)

zlib is a Ruby interface for the zlib compression/decompression library. Versions 3.0.0 and below, 3.1.0, 3.1.1, 3.2.0 and 3.2.1 contain a buffer overflow vulnerability in the Zlib::GzipReader. The zstream_buffer_ungets function prepends caller-provided bytes ahead of previously produced output but fails to guarantee the backing Ruby string has enough capacity before the memmove shifts the existing data. This can lead to memory corruption when the buffer length exceeds capacity. This issue has been fixed in versions 3.0.1, 3.1.2 and 3.2.3.(CVE-2026-27820)

Ruby is a fast and easy interpreted scripting language for object-oriented programming. It has many functions for processing text Files and perform system management tasks (such as Perl).

Security Fix(es):

The attack vector is a potential Denial of Service (DoS). The vulnerability is caused by an insufficient check on the length of a decompressed domain name within a DNS packet.

An attacker can craft a malicious DNS packet containing a highly compressed domain name. When the resolv library parses such a packet, the name decompression process consumes a large amount of CPU resources, as the library does not limit the resulting length of the name.

This resource consumption can cause the application thread to become unresponsive, resulting in a Denial of Service condition.(CVE-2025-24294)

zlib is a Ruby interface for the zlib compression/decompression library. Versions 3.0.0 and below, 3.1.0, 3.1.1, 3.2.0 and 3.2.1 contain a buffer overflow vulnerability in the Zlib::GzipReader. The zstream_buffer_ungets function prepends caller-provided bytes ahead of previously produced output but fails to guarantee the backing Ruby string has enough capacity before the memmove shifts the existing data. This can lead to memory corruption when the buffer length exceeds capacity. This issue has been fixed in versions 3.0.1, 3.1.2 and 3.2.3.(CVE-2026-27820)

Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to 0.6.5 and 0.5.15, several Net::IMAP commands accept a "raw data" argument that is sent verbatim after validation to prevent command injection. However, if a server does not support non-synchronizing literals, it may still be possible to inject arbitrary IMAP commands inside non-synchronizing literals. A server without support for non-synchronizing literals may interpret the "+}\r\n" as the end of a malformed command line and respond with a tagged BAD. In that case, the contents of the literal will be interpreted as one or more new pipelined commands, allowing a CRLF command injection attack to succeed. This affects criteria for #search and #uid_search; search_keys for #sort, #thread, #uid_sort, and #uid_thread; and attr for #fetch and #uid_fetch. This vulnerability is fixed in 0.6.5 and 0.5.15.(CVE-2026-47240)

Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to 0.6.5 and 0.5.15, several Net::IMAP commands accept a raw string argument which is only validated to prevent CRLF injection and then sent verbatim. If this string is derived from user-controlled input, an attacker can force the next command to be absorbed as a continuation of the first command. This will cause the first command to eventually fail, but also prevents it from returning until another command is sent (from another thread). That other command will not return until the connection is closed. This vulnerability is fixed in 0.6.5 and 0.5.15.(CVE-2026-47241)

Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to 0.6.5 and 0.5.15, when Net::IMAP#id is called with a hash argument, although the ID field value strings are correctly quoted (escaping quoted specials), they were not validated to prohibit CRLF sequences. While Net::IMAP#enable does process its arguments for aliases, it does not validate them as valid atoms (or as a list of valid atoms). The #to_s value is sent verbatim. Arguments to either command could be used by an attacker to inject arbitrary IMAP commands. This vulnerability is fixed in 0.6.5 and 0.5.15.(CVE-2026-47242)

Ruby is a fast and easy interpreted scripting language for object-oriented programming. It has many functions for processing text Files and perform system management tasks (such as Perl).

Security Fix(es):

The attack vector is a potential Denial of Service (DoS). The vulnerability is caused by an insufficient check on the length of a decompressed domain name within a DNS packet.

An attacker can craft a malicious DNS packet containing a highly compressed domain name. When the resolv library parses such a packet, the name decompression process consumes a large amount of CPU resources, as the library does not limit the resulting length of the name.

This resource consumption can cause the application thread to become unresponsive, resulting in a Denial of Service condition.(CVE-2025-24294)

zlib is a Ruby interface for the zlib compression/decompression library. Versions 3.0.0 and below, 3.1.0, 3.1.1, 3.2.0 and 3.2.1 contain a buffer overflow vulnerability in the Zlib::GzipReader. The zstream_buffer_ungets function prepends caller-provided bytes ahead of previously produced output but fails to guarantee the backing Ruby string has enough capacity before the memmove shifts the existing data. This can lead to memory corruption when the buffer length exceeds capacity. This issue has been fixed in versions 3.0.1, 3.1.2 and 3.2.3.(CVE-2026-27820)

Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to 0.6.5 and 0.5.15, several Net::IMAP commands accept a "raw data" argument that is sent verbatim after validation to prevent command injection. However, if a server does not support non-synchronizing literals, it may still be possible to inject arbitrary IMAP commands inside non-synchronizing literals. A server without support for non-synchronizing literals may interpret the "+}\r\n" as the end of a malformed command line and respond with a tagged BAD. In that case, the contents of the literal will be interpreted as one or more new pipelined commands, allowing a CRLF command injection attack to succeed. This affects criteria for #search and #uid_search; search_keys for #sort, #thread, #uid_sort, and #uid_thread; and attr for #fetch and #uid_fetch. This vulnerability is fixed in 0.6.5 and 0.5.15.(CVE-2026-47240)

Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to 0.6.5 and 0.5.15, several Net::IMAP commands accept a raw string argument which is only validated to prevent CRLF injection and then sent verbatim. If this string is derived from user-controlled input, an attacker can force the next command to be absorbed as a continuation of the first command. This will cause the first command to eventually fail, but also prevents it from returning until another command is sent (from another thread). That other command will not return until the connection is closed. This vulnerability is fixed in 0.6.5 and 0.5.15.(CVE-2026-47241)

Ruby is an extensible, interpreted, object-oriented, scripting language. It has features to process text files and to perform system management tasks.

Security Fix(es):

• zlib: zlib: Memory corruption via buffer overflow in Zlib::GzipReader (CVE-2026-27820)

• net-imap: Net::IMAP: Arbitrary IMAP command injection via CRLF sequences in unvalidated input (CVE-2026-42257)

• ruby/net-imap: ruby: Net::IMAP: Denial of Service via large iteration count in SCRAM authentication (CVE-2026-42256)

• net-imap: Net::IMAP: Command injection via non-synchronizing literals (CVE-2026-47240)

• net-imap: Net::IMAP: Arbitrary IMAP command injection due to improper input validation (CVE-2026-47242)

• net-imap: rubygem-net-imap: Net::IMAP: Denial of Service via malformed command input (CVE-2026-47241)

Bug Fix(es) and Enhancement(s):

• ruby:3.3/ruby: Rebase to the latest Ruby 3.3 release [rhel-8] (JIRA:Rocky Linux-170929)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Ruby is the interpreted scripting language for quick and easy object-oriented programming. It has many features to process text files and to do system management tasks (as in Perl). It is simple, straight-forward, and extensible.

Security Fix(es):

• zlib: zlib: Memory corruption via buffer overflow in Zlib::GzipReader (CVE-2026-27820)

• net-imap: Net::IMAP: Arbitrary IMAP command injection via CRLF sequences in unvalidated input (CVE-2026-42257)

• ruby/net-imap: ruby: Net::IMAP: Denial of Service via large iteration count in SCRAM authentication (CVE-2026-42256)

• net-imap: Net::IMAP: Command injection via non-synchronizing literals (CVE-2026-47240)

• net-imap: Net::IMAP: Arbitrary IMAP command injection due to improper input validation (CVE-2026-47242)

• net-imap: rubygem-net-imap: Net::IMAP: Denial of Service via malformed command input (CVE-2026-47241)

Bug Fix(es) and Enhancement(s):

• ruby4.0: Rebase to the latest Ruby 4.0 release [rhel-10.2.z] (JIRA:Rocky Linux-211310)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Ruby is an extensible, interpreted, object-oriented, scripting language. It has features to process text files and to perform system management tasks.

Security Fix(es):

• zlib: zlib: Memory corruption via buffer overflow in Zlib::GzipReader (CVE-2026-27820)

• net-imap: Net::IMAP: Arbitrary IMAP command injection via CRLF sequences in unvalidated input (CVE-2026-42257)

• ruby/net-imap: ruby: Net::IMAP: Denial of Service via large iteration count in SCRAM authentication (CVE-2026-42256)

• net-imap: Net::IMAP: Command injection via non-synchronizing literals (CVE-2026-47240)

• net-imap: Net::IMAP: Arbitrary IMAP command injection due to improper input validation (CVE-2026-47242)

• net-imap: rubygem-net-imap: Net::IMAP: Denial of Service via malformed command input (CVE-2026-47241)

Bug Fix(es) and Enhancement(s):

• ruby: Rebase to the latest Ruby 3.3 release [rhel-10.2.z] (JIRA:Rocky Linux-211300)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Ruby is an extensible, interpreted, object-oriented, scripting language. It has features to process text files and to perform system management tasks.

Security Fix(es):

• zlib: zlib: Memory corruption via buffer overflow in Zlib::GzipReader (CVE-2026-27820)

• net-imap: Net::IMAP: Arbitrary IMAP command injection via CRLF sequences in unvalidated input (CVE-2026-42257)

• ruby/net-imap: ruby: Net::IMAP: Denial of Service via large iteration count in SCRAM authentication (CVE-2026-42256)

• net-imap: Net::IMAP: Command injection via non-synchronizing literals (CVE-2026-47240)

• net-imap: Net::IMAP: Arbitrary IMAP command injection due to improper input validation (CVE-2026-47242)

• net-imap: rubygem-net-imap: Net::IMAP: Denial of Service via malformed command input (CVE-2026-47241)

Bug Fix(es) and Enhancement(s):

• ruby:4.0/ruby: Rebase to the latest Ruby 4.0 release [rhel-9.8.z] (JIRA:Rocky Linux-211301)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Ruby is an extensible, interpreted, object-oriented, scripting language. It has features to process text files and to perform system management tasks.

Security Fix(es):

• zlib: zlib: Memory corruption via buffer overflow in Zlib::GzipReader (CVE-2026-27820)

• net-imap: Net::IMAP: Arbitrary IMAP command injection via CRLF sequences in unvalidated input (CVE-2026-42257)

• ruby/net-imap: ruby: Net::IMAP: Denial of Service via large iteration count in SCRAM authentication (CVE-2026-42256)

• net-imap: Net::IMAP: Command injection via non-synchronizing literals (CVE-2026-47240)

• net-imap: Net::IMAP: Arbitrary IMAP command injection due to improper input validation (CVE-2026-47242)

• net-imap: rubygem-net-imap: Net::IMAP: Denial of Service via malformed command input (CVE-2026-47241)

Bug Fix(es) and Enhancement(s):

• ruby:3.3/ruby: Rebase to the latest Ruby 3.3 release [rhel-9.8.z] (JIRA:Rocky Linux-171335)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

zlib is a Ruby interface for the zlib compression/decompression library. Versions 3.0.0 and below, 3.1.0, 3.1.1, 3.2.0 and 3.2.1 contain a buffer overflow vulnerability in the Zlib::GzipReader. The zstream_buffer_ungets function prepends caller-provided bytes ahead of previously produced output but fails to guarantee the backing Ruby string has enough capacity before the memmove shifts the existing data. This can lead to memory corruption when the buffer length exceeds capacity. This issue has been fixed in versions 3.0.1, 3.1.2 and 3.2.3.

Ruby is an extensible, interpreted, object-oriented, scripting language. It has features to process text files and to perform system management tasks.

Security Fix(es):

• zlib: zlib: Memory corruption via buffer overflow in Zlib::GzipReader (CVE-2026-27820)
• net-imap: Net::IMAP: Arbitrary IMAP command injection via CRLF sequences in unvalidated input (CVE-2026-42257)
• ruby/net-imap: ruby: Net::IMAP: Denial of Service via large iteration count in SCRAM authentication (CVE-2026-42256)
• net-imap: Net::IMAP: Command injection via non-synchronizing literals (CVE-2026-47240)
• net-imap: Net::IMAP: Arbitrary IMAP command injection due to improper input validation (CVE-2026-47242)
• net-imap: rubygem-net-imap: Net::IMAP: Denial of Service via malformed command input (CVE-2026-47241)

Bug Fix(es) and Enhancement(s):

• ruby:3.3/ruby: Rebase to the latest Ruby 3.3 release [almalinux-8] (JIRA:AlmaLinux-170929)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Ruby is the interpreted scripting language for quick and easy object-oriented programming. It has many features to process text files and to do system management tasks (as in Perl). It is simple, straight-forward, and extensible.

Security Fix(es):

• zlib: zlib: Memory corruption via buffer overflow in Zlib::GzipReader (CVE-2026-27820)
• net-imap: Net::IMAP: Arbitrary IMAP command injection via CRLF sequences in unvalidated input (CVE-2026-42257)
• ruby/net-imap: ruby: Net::IMAP: Denial of Service via large iteration count in SCRAM authentication (CVE-2026-42256)
• net-imap: Net::IMAP: Command injection via non-synchronizing literals (CVE-2026-47240)
• net-imap: Net::IMAP: Arbitrary IMAP command injection due to improper input validation (CVE-2026-47242)
• net-imap: rubygem-net-imap: Net::IMAP: Denial of Service via malformed command input (CVE-2026-47241)

Bug Fix(es) and Enhancement(s):

• ruby4.0: Rebase to the latest Ruby 4.0 release [almalinux-10.2.z] (JIRA:AlmaLinux-211310)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Ruby is an extensible, interpreted, object-oriented, scripting language. It has features to process text files and to perform system management tasks.

Security Fix(es):

• zlib: zlib: Memory corruption via buffer overflow in Zlib::GzipReader (CVE-2026-27820)
• net-imap: Net::IMAP: Arbitrary IMAP command injection via CRLF sequences in unvalidated input (CVE-2026-42257)
• ruby/net-imap: ruby: Net::IMAP: Denial of Service via large iteration count in SCRAM authentication (CVE-2026-42256)
• net-imap: Net::IMAP: Command injection via non-synchronizing literals (CVE-2026-47240)
• net-imap: Net::IMAP: Arbitrary IMAP command injection due to improper input validation (CVE-2026-47242)
• net-imap: rubygem-net-imap: Net::IMAP: Denial of Service via malformed command input (CVE-2026-47241)

Bug Fix(es) and Enhancement(s):

• ruby: Rebase to the latest Ruby 3.3 release [almalinux-10.2.z] (JIRA:AlmaLinux-211300)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Ruby is an extensible, interpreted, object-oriented, scripting language. It has features to process text files and to perform system management tasks.

Security Fix(es):

• zlib: zlib: Memory corruption via buffer overflow in Zlib::GzipReader (CVE-2026-27820)
• net-imap: Net::IMAP: Arbitrary IMAP command injection via CRLF sequences in unvalidated input (CVE-2026-42257)
• ruby/net-imap: ruby: Net::IMAP: Denial of Service via large iteration count in SCRAM authentication (CVE-2026-42256)
• net-imap: Net::IMAP: Command injection via non-synchronizing literals (CVE-2026-47240)
• net-imap: Net::IMAP: Arbitrary IMAP command injection due to improper input validation (CVE-2026-47242)
• net-imap: rubygem-net-imap: Net::IMAP: Denial of Service via malformed command input (CVE-2026-47241)

Bug Fix(es) and Enhancement(s):

• ruby:4.0/ruby: Rebase to the latest Ruby 4.0 release [almalinux-9.8.z] (JIRA:AlmaLinux-211301)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Ruby is an extensible, interpreted, object-oriented, scripting language. It has features to process text files and to perform system management tasks.

Security Fix(es):

• zlib: zlib: Memory corruption via buffer overflow in Zlib::GzipReader (CVE-2026-27820)
• net-imap: Net::IMAP: Arbitrary IMAP command injection via CRLF sequences in unvalidated input (CVE-2026-42257)
• ruby/net-imap: ruby: Net::IMAP: Denial of Service via large iteration count in SCRAM authentication (CVE-2026-42256)
• net-imap: Net::IMAP: Command injection via non-synchronizing literals (CVE-2026-47240)
• net-imap: Net::IMAP: Arbitrary IMAP command injection due to improper input validation (CVE-2026-47242)
• net-imap: rubygem-net-imap: Net::IMAP: Denial of Service via malformed command input (CVE-2026-47241)

Bug Fix(es) and Enhancement(s):

• ruby:3.3/ruby: Rebase to the latest Ruby 3.3 release [almalinux-9.8.z] (JIRA:AlmaLinux-171335)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

zlib is a Ruby interface for the zlib compression/decompression library. Versions 3.0.0 and below, 3.1.0, 3.1.1, 3.2.0 and 3.2.1 contain a buffer overflow vulnerability in the Zlib::GzipReader. The zstream_buffer_ungets function prepends caller-provided bytes ahead of previously produced output but fails to guarantee the backing Ruby string has enough capacity before the memmove shifts the existing data. This can lead to memory corruption when the buffer length exceeds capacity. This issue has been fixed in versions 3.0.1, 3.1.2 and 3.2.3.

• CVE-2026-27820: zlib: fix buffer overflow in Zlib::GzipReader#ungetc by always growing the output buffer before the memmove

• CVE-2026-27820: zlib: fix buffer overflow in Zlib::GzipReader#ungetc by always growing the output buffer before the memmove

• CVE-2026-27820: fix buffer overflow in Zlib::GzipReader#ungetc
• Skip unresolvable GIDs in TestProcess#test_execopts_gid (build env workaround)

This update for ruby3.4 fixes the following issues:

• CVE-2025-58767: denial of service when parsing XML containing multiple XML declarations (bsc#1250016).
• CVE-2026-27820: insufficient checks in zstream_buffer_ungets can lead to a buffer overflow (bsc#1259239).
• CVE-2026-41316: erb: @_init deserialization guard bypass via def_module / def_method / def_class (bsc#1262441).
• CVE-2026-42258: ruby: Net:IMAP: IMAP Command Injection via Symbol Arguments (bsc#1268011).
• CVE-2026-47240: Net:IMAP: Command Injection via non-synchronizing literal in "raw" argument (bsc#1268337).
• CVE-2026-47241: Net:IMAP: Denial of Service via incomplete raw argument validation (bsc#1268338).
• CVE-2026-47242: Net:IMAP: Command Injection via ID and ENABLE command arguments (bsc#1268339).
• CVE-2025-61594: rubygem-uri: URI concatenation with the plus operator can cause credential disclosure (bsc#1255833).

Changes for ruby3.4:

• Update to 3.4.10.

• Update to 3.4.9:

• Bug #21715: Miscompilation on x86-64-v2 due to undefined behavior in search_nonascii in string.c - Ruby - Ruby Issue Tracking System

• Bug #21787: IO::Buffer Integer Overflow in Range Validation Leads to Out-of-Bounds Memory Access - Ruby - Ruby Issue

• Bug #21757: Splatted args array is mutated when passing unexpected kwargs - Ruby - Ruby Issue Tracking System

• Bug #21326: Instruction generation differences between parse.y and prism for def a(x, ...); b(...); end - Ruby - Ruby Issue

• Bug #21814: 0.pow(2,-9999999999999999990) should be zero - Ruby

• Ruby Issue Tracking System

• Bug #21819: A Data object should be frozen even if it has no members - Ruby - Ruby Issue Tracking System

• Bug #21811: Fix underflow in Array#pack - Ruby - Ruby Issue

• Bug #21838: Rails seeing degradation (20% slowdown) related to Revision 079ef92b "Implement global allocatable slots and empty pages" (from Sep 5 2024) - Ruby - Ruby Issue Tracking System

• Bug #21931: GC Crash in String#% (backport 726205b354d1068147719fb42e1de743f1838ef1) - Ruby - Ruby Issue

• Bug #21860: Process.fork: the child may deadlock on th->interrupt_lock in threadptr_interrupt_exec_cleanup - Ruby - Ruby Issue Tracking System

• Bug #21873: UnboundMethod#== returns false for methods from included/extended modules - Ruby - Ruby Issue Tracking System

• Update to 3.4.8:

  • Bug #21629: Ruby-3.4.7 prints -Wdefault-const-init-field-unsafe warnings on clang / llvm 21 - Ruby - Ruby Issue Tracking System

• Bug #21626: Backport WASI setjmp handler memory leak fixes - Ruby - Ruby Issue Tracking System

• Bug #21631: Backport openssl gem bugfix releases - Ruby - Ruby Issue Tracking System

• Bug #21632: Backport REXML CVE-2025-58767 fix (bsc#1250016) -

• Bug #21644: Stack consistency error for the newrange INSN peephole optimization with chilled string - Ruby - Ruby Issue

• Bug #21668: Improve performance of UnicodeNormalize.canonical_ordering_one - Ruby - Ruby Issue

• Bug #21638: Ractor-local $DEBUG is not marked - Ruby - Ruby

• Bug #21652: Marshal#dump documentation out-of-date/unclear regarding Data class - Ruby - Ruby Issue Tracking System

• Bug #13671: Regexp with lookbehind and case-insensitivity raises RegexpError only on strings with certain characters -

• Bug #21625: Allow IO#wait_readable together with IO#ungetc even in text mode - Ruby - Ruby Issue Tracking System

• Bug #21671: Rails CI raises Assertion Failed: rbimpl_rstring_getmem:RB_TYPE_P(str, RUBY_T_STRING): actual type: 26 with "-DENABLE_PATH_CHECK=0 -DRUBY_DEBUG=1" enabled -

• Update next stable version to 4.0 from 3.5 by hsbt . Pull Request #15146

• Bug #21679: Segfault when ruby calls pthread_detach in rb_getnameinfo - Ruby - Ruby Issue Tracking System

• Bug #21694: Crash when looking up super method from BasicObject

• Ruby - Ruby Issue Tracking System

• Bug #21707: Destructuring assignment of SimpleDelegator wrapped array bug with YJIT - Ruby - Ruby Issue Tracking System

• Bug #21265: Crash when proc from…

This update for ruby2.5 fixes the following issues:

• CVE-2024-49761: ReDoS vulnerability in REXML gem (bsc#1232440 bsc#1232441).
• CVE-2025-58767: denial of service when parsing XML containing multiple XML declarations (bsc#1250016).
• CVE-2026-27820: insufficient checks in zstream_buffer_ungets can lead to a buffer overflow (bsc#1259239).

It was discovered that the Net::IMAP client in Ruby did not properly sanitize Symbol arguments passed to IMAP commands. A remote attacker controlling a malicious IMAP server, or able to influence command arguments, could use this to inject arbitrary IMAP commands via CRLF sequences. (CVE-2026-42258)

It was discovered that the Zlib::GzipReader in Ruby did not correctly ensure sufficient buffer capacity in the zstream_buffer_ungets function. An attacker could use this to craft a gzip stream that, when processed, could cause a buffer overflow, resulting in memory corruption and possibly arbitrary code execution. (CVE-2026-27820)