CVE-2025-46727

Summary

Rack::QueryParser parses query strings and application/x-www-form-urlencoded bodies into Ruby data structures without imposing any limit on the number of parameters, allowing attackers to send requests with extremely large numbers of parameters.

Details

The vulnerability arises because Rack::QueryParser iterates over each &-separated key-value pair and adds it to a Hash without enforcing an upper bound on the total number of parameters. This allows an attacker to send a single request containing hundreds of thousands (or more) of parameters, which consumes excessive memory and CPU during parsing.

Impact

An attacker can trigger denial of service by sending specifically crafted HTTP requests, which can cause memory exhaustion or pin CPU resources, stalling or crashing the Rack server. This results in full service disruption until the affected worker is restarted.

Mitigation

• Update to a version of Rack that limits the number of parameters parsed, or
• Use middleware to enforce a maximum query string size or parameter count, or
• Employ a reverse proxy (such as Nginx) to limit request sizes and reject oversized query strings or bodies.

Limiting request body sizes and query string lengths at the web server or CDN level is an effective mitigation.

Rack provides a minimal, modular and adaptable interface for developing web applications in Ruby. By wrapping HTTP requests and responses in the simplest way possible, it unifies and distills the API for web servers, web frameworks, and software in between (the so-called middleware) into a single method call.

Security Fix(es):

Rack is a modular Ruby web server interface. Prior to versions 2.2.14, 3.0.16, and 3.1.14, Rack::QueryParser parses query strings and application/x-www-form-urlencoded bodies into Ruby data structures without imposing any limit on the number of parameters, allowing attackers to send requests with extremely large numbers of parameters. The vulnerability arises because Rack::QueryParser iterates over each &-separated key-value pair and adds it to a Hash without enforcing an upper bound on the total number of parameters. This allows an attacker to send a single request containing hundreds of thousands (or more) of parameters, which consumes excessive memory and CPU during parsing. An attacker can trigger denial of service by sending specifically crafted HTTP requests, which can cause memory exhaustion or pin CPU resources, stalling or crashing the Rack server. This results in full service disruption until the affected worker is restarted. Versions 2.2.14, 3.0.16, and 3.1.14 fix the issue. Some other mitigations are available. One may use middleware to enforce a maximum query string size or parameter count, or employ a reverse proxy (such as Nginx) to limit request sizes and reject oversized query strings or bodies. Limiting request body sizes and query string lengths at the web server or CDN level is an effective mitigation.(CVE-2025-46727)

Rack provides a minimal, modular and adaptable interface for developing web applications in Ruby. By wrapping HTTP requests and responses in the simplest way possible, it unifies and distills the API for web servers, web frameworks, and software in between (the so-called middleware) into a single method call.

Security Fix(es):

Rack is a modular Ruby web server interface. Prior to versions 2.2.14, 3.0.16, and 3.1.14, Rack::QueryParser parses query strings and application/x-www-form-urlencoded bodies into Ruby data structures without imposing any limit on the number of parameters, allowing attackers to send requests with extremely large numbers of parameters. The vulnerability arises because Rack::QueryParser iterates over each &-separated key-value pair and adds it to a Hash without enforcing an upper bound on the total number of parameters. This allows an attacker to send a single request containing hundreds of thousands (or more) of parameters, which consumes excessive memory and CPU during parsing. An attacker can trigger denial of service by sending specifically crafted HTTP requests, which can cause memory exhaustion or pin CPU resources, stalling or crashing the Rack server. This results in full service disruption until the affected worker is restarted. Versions 2.2.14, 3.0.16, and 3.1.14 fix the issue. Some other mitigations are available. One may use middleware to enforce a maximum query string size or parameter count, or employ a reverse proxy (such as Nginx) to limit request sizes and reject oversized query strings or bodies. Limiting request body sizes and query string lengths at the web server or CDN level is an effective mitigation.(CVE-2025-46727)

Rack provides a minimal, modular and adaptable interface for developing web applications in Ruby. By wrapping HTTP requests and responses in the simplest way possible, it unifies and distills the API for web servers, web frameworks, and software in between (the so-called middleware) into a single method call.

Security Fix(es):

Rack is a modular Ruby web server interface. Prior to versions 2.2.14, 3.0.16, and 3.1.14, Rack::QueryParser parses query strings and application/x-www-form-urlencoded bodies into Ruby data structures without imposing any limit on the number of parameters, allowing attackers to send requests with extremely large numbers of parameters. The vulnerability arises because Rack::QueryParser iterates over each &-separated key-value pair and adds it to a Hash without enforcing an upper bound on the total number of parameters. This allows an attacker to send a single request containing hundreds of thousands (or more) of parameters, which consumes excessive memory and CPU during parsing. An attacker can trigger denial of service by sending specifically crafted HTTP requests, which can cause memory exhaustion or pin CPU resources, stalling or crashing the Rack server. This results in full service disruption until the affected worker is restarted. Versions 2.2.14, 3.0.16, and 3.1.14 fix the issue. Some other mitigations are available. One may use middleware to enforce a maximum query string size or parameter count, or employ a reverse proxy (such as Nginx) to limit request sizes and reject oversized query strings or bodies. Limiting request body sizes and query string lengths at the web server or CDN level is an effective mitigation.(CVE-2025-46727)

Rack provides a minimal, modular and adaptable interface for developing web applications in Ruby. By wrapping HTTP requests and responses in the simplest way possible, it unifies and distills the API for web servers, web frameworks, and software in between (the so-called middleware) into a single method call.

Security Fix(es):

Rack is a modular Ruby web server interface. Prior to versions 2.2.14, 3.0.16, and 3.1.14, Rack::QueryParser parses query strings and application/x-www-form-urlencoded bodies into Ruby data structures without imposing any limit on the number of parameters, allowing attackers to send requests with extremely large numbers of parameters. The vulnerability arises because Rack::QueryParser iterates over each &-separated key-value pair and adds it to a Hash without enforcing an upper bound on the total number of parameters. This allows an attacker to send a single request containing hundreds of thousands (or more) of parameters, which consumes excessive memory and CPU during parsing. An attacker can trigger denial of service by sending specifically crafted HTTP requests, which can cause memory exhaustion or pin CPU resources, stalling or crashing the Rack server. This results in full service disruption until the affected worker is restarted. Versions 2.2.14, 3.0.16, and 3.1.14 fix the issue. Some other mitigations are available. One may use middleware to enforce a maximum query string size or parameter count, or employ a reverse proxy (such as Nginx) to limit request sizes and reject oversized query strings or bodies. Limiting request body sizes and query string lengths at the web server or CDN level is an effective mitigation.(CVE-2025-46727)

Rack provides a minimal, modular and adaptable interface for developing web applications in Ruby. By wrapping HTTP requests and responses in the simplest way possible, it unifies and distills the API for web servers, web frameworks, and software in between (the so-called middleware) into a single method call.

Security Fix(es):

Rack is a modular Ruby web server interface. Prior to versions 2.2.14, 3.0.16, and 3.1.14, Rack::QueryParser parses query strings and application/x-www-form-urlencoded bodies into Ruby data structures without imposing any limit on the number of parameters, allowing attackers to send requests with extremely large numbers of parameters. The vulnerability arises because Rack::QueryParser iterates over each &-separated key-value pair and adds it to a Hash without enforcing an upper bound on the total number of parameters. This allows an attacker to send a single request containing hundreds of thousands (or more) of parameters, which consumes excessive memory and CPU during parsing. An attacker can trigger denial of service by sending specifically crafted HTTP requests, which can cause memory exhaustion or pin CPU resources, stalling or crashing the Rack server. This results in full service disruption until the affected worker is restarted. Versions 2.2.14, 3.0.16, and 3.1.14 fix the issue. Some other mitigations are available. One may use middleware to enforce a maximum query string size or parameter count, or employ a reverse proxy (such as Nginx) to limit request sizes and reject oversized query strings or bodies. Limiting request body sizes and query string lengths at the web server or CDN level is an effective mitigation.(CVE-2025-46727)

Rack provides a minimal, modular and adaptable interface for developing web applications in Ruby. By wrapping HTTP requests and responses in the simplest way possible, it unifies and distills the API for web servers, web frameworks, and software in between (the so-called middleware) into a single method call.

Security Fix(es):

Rack is a modular Ruby web server interface. Prior to versions 2.2.14, 3.0.16, and 3.1.14, Rack::QueryParser parses query strings and application/x-www-form-urlencoded bodies into Ruby data structures without imposing any limit on the number of parameters, allowing attackers to send requests with extremely large numbers of parameters. The vulnerability arises because Rack::QueryParser iterates over each &-separated key-value pair and adds it to a Hash without enforcing an upper bound on the total number of parameters. This allows an attacker to send a single request containing hundreds of thousands (or more) of parameters, which consumes excessive memory and CPU during parsing. An attacker can trigger denial of service by sending specifically crafted HTTP requests, which can cause memory exhaustion or pin CPU resources, stalling or crashing the Rack server. This results in full service disruption until the affected worker is restarted. Versions 2.2.14, 3.0.16, and 3.1.14 fix the issue. Some other mitigations are available. One may use middleware to enforce a maximum query string size or parameter count, or employ a reverse proxy (such as Nginx) to limit request sizes and reject oversized query strings or bodies. Limiting request body sizes and query string lengths at the web server or CDN level is an effective mitigation.(CVE-2025-46727)

The pcs packages provide a command-line configuration system for the Pacemaker and Corosync utilities.

Security Fix(es):

• rubygem-rack: Unbounded-Parameter DoS in Rack::QueryParser (CVE-2025-46727)

• tornado: Tornado Multipart Form-Data Denial of Service (CVE-2025-47287)

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.

The pcs packages provide a command-line configuration system for the Pacemaker and Corosync utilities.

Security Fix(es):

• rubygem-rack: Unbounded-Parameter DoS in Rack::QueryParser (CVE-2025-46727)

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.

Rack is a modular Ruby web server interface. Prior to versions 2.2.14, 3.0.16, and 3.1.14, Rack::QueryParser parses query strings and application/x-www-form-urlencoded bodies into Ruby data structures without imposing any limit on the number of parameters, allowing attackers to send requests with extremely large numbers of parameters. The vulnerability arises because Rack::QueryParser iterates over each &-separated key-value pair and adds it to a Hash without enforcing an upper bound on the total number of parameters. This allows an attacker to send a single request containing hundreds of thousands (or more) of parameters, which consumes excessive memory and CPU during parsing. An attacker can trigger denial of service by sending specifically crafted HTTP requests, which can cause memory exhaustion or pin CPU resources, stalling or crashing the Rack server. This results in full service disruption until the affected worker is restarted. Versions 2.2.14, 3.0.16, and 3.1.14 fix the issue. Some other mitigations are available. One may use middleware to enforce a maximum query string size or parameter count, or employ a reverse proxy (such as Nginx) to limit request sizes and reject oversized query strings or bodies. Limiting request body sizes and query string lengths at the web server or CDN level is an effective mitigation.

The pcs packages provide a command-line configuration system for the Pacemaker and Corosync utilities.

Security Fix(es):

• rubygem-rack: Unbounded-Parameter DoS in Rack::QueryParser (CVE-2025-46727)
• tornado: Tornado Multipart Form-Data Denial of Service (CVE-2025-47287)

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.

• CVE-2025-46727: unbounded query parsing in bundled rack; a body of repeated keys was parsed in full, exhausting memory. Capped by rack's new query bytesize and parameter-count limits, which pcsd turns into an HTTP 400
• CVE-2025-59830: the same unbounded query parse reached through ';' separated query strings, which rack's parameter counter did not count
• CVE-2025-61770: multipart parsing in bundled rack read the whole request body searching for a boundary that never arrived
• CVE-2025-61771: multipart parsing in bundled rack retained an unbounded non-file field in memory
• CVE-2025-61772: multipart mime part headers in bundled rack were read with no size limit
• CVE-2025-61919: Rack::Request#POST read the entire request body before any limit applied, so a 64 MB body was fully buffered
• CVE-2024-49761: quadratic regular expression in bundled rexml BaseParser#unnormalize; a long run of zeros in a hex character reference made the parser hang
• CVE-2024-52804: quadratic cookie unquoting in bundled tornado _unquote_cookie, which rescanned the value from each escape
• CVE-2025-47287: malformed multipart/form-data in bundled tornado logged a warning per bad part instead of rejecting the request, flooding the log
• CVE-2026-31958: unbounded part count and part header size in bundled tornado multipart parsing
• Stop forwarding client HTTP headers from the Tornado front end to the Ruby part of pcsd, which only ever needed the cookie and the content type

• Update bundled rubygem rack to 2.2.20
• CVE-2024-25126: fix ReDoS in Rack::MediaType content type parsing
• CVE-2024-26141: fix response amplification from crafted Range headers
• CVE-2024-26146: fix ReDoS in Accept and Forwarded header parsing
• CVE-2025-46727: fix unbounded parameter count in Rack::QueryParser
• CVE-2025-59830: fix params_limit bypass via semicolon-separated parameters
• CVE-2025-61770: fix unbounded multipart preamble buffering
• CVE-2025-61771: fix unbounded buffering of non-file multipart fields
• CVE-2025-61772: fix unbounded multipart part header buffering
• CVE-2025-61919: fix unbounded form body read in Rack::Request#POST
• Handle Rack::QueryParser::QueryLimitError in pcsd, returning 400 instead of 500
• CVE-2026-31958: cap multipart part count and part header size in bundled tornado
• Disable multipart request parsing in pcsd, which does not use it
• Drop i686 from ExclusiveArch: the bundled web UI needs npm at build time and npm has no i686 build, so the i686 buildroot cannot be created

• Update bundled rubygem rack to 2.2.20
• CVE-2024-25126: fix ReDoS in Rack::MediaType content type parsing
• CVE-2024-26141: fix response amplification from crafted Range headers
• CVE-2024-26146: fix ReDoS in Accept and Forwarded header parsing
• CVE-2025-46727: fix unbounded parameter count in Rack::QueryParser
• CVE-2025-59830: fix params_limit bypass via semicolon-separated parameters
• CVE-2025-61770: fix unbounded multipart preamble buffering
• CVE-2025-61771: fix unbounded buffering of non-file multipart fields
• CVE-2025-61772: fix unbounded multipart part header buffering
• CVE-2025-61919: fix unbounded form body read in Rack::Request#POST
• Handle Rack::QueryParser::QueryLimitError in pcsd, returning 400 instead of 500
• CVE-2026-31958: cap multipart part count and part header size in bundled tornado
• Disable multipart request parsing in pcsd, which does not use it
• Drop i686 from ExclusiveArch: the bundled web UI needs npm at build time and npm has no i686 build, so the i686 buildroot cannot be created

• Fix CVE-2025-46727: limit number and bytesize of query parameters in bundled rubygem rack
• Fix CVE-2025-61919: bound the read of urlencoded request bodies in bundled rubygem rack
• Fix CVE-2025-61771: limit multipart data retained in memory in bundled rubygem rack
• Fix CVE-2025-61772: limit the multipart part header size in bundled rubygem rack
• Skip the pcs tests that need pacemaker >= 1.1.23 when the build root has an older one (CloudLinux 7)

Unbounded-Parameter DoS in Rack::QueryParser. (CVE-2025-46727) ReDoS Vulnerability in Rack::Multipart handle_mime_head. (CVE-2025-49007) Rack QueryParser has an unsafe default allowing params_limit bypass via semicolon-separated parameters. (CVE-2025-59830) Rack's unbounded multipart preamble buffering enables DoS (memory exhaustion). (CVE-2025-61770) Rack's multipart parser buffers large non‑file fields entirely in memory, enabling DoS (memory exhaustion). (CVE-2025-61771) Rack's multipart parser buffers unbounded per-part headers, enabling DoS (memory exhaustion). (CVE-2025-61772) Rack is vulnerable to a memory-exhaustion DoS through unbounded URL-encoded body parsing. (CVE-2025-61919) Rack has Possible Information Disclosure Vulnerability. (CVE-2025-61780)

These are all security issues fixed in the ruby3.4-rubygem-rack-2.2-2.2.14-1.1 package on the GA media of openSUSE Tumbleweed.

These are all security issues fixed in the ruby4.0-rubygem-rack-2.2-2.2.22-1.1 package on the GA media of openSUSE Tumbleweed.

This update for rubygem-rack fixes the following issues:

• CVE-2025-46727: possible memory exhaustion due to unbounded parameter parsing in Rack::QueryParser (bsc#1242894).
• CVE-2025-32441: deleted sessions can be restored and occupied by unauthenticated users when the Rack::Session::Pool middleware is being used (bsc#1242899).

This update for rubygem-rack fixes the following issues:

• CVE-2025-46727: possible memory exhaustion due to unbounded parameter parsing in Rack::QueryParser (bsc#1242894).
• CVE-2025-32441: deleted sessions can be restored and occupied by unauthenticated users when the Rack::Session::Pool middleware is being used (bsc#1242899).

This update for rmt-server fixes the following issues:

• Update to version 2.23
• CVE-2025-46727: Fixed Unbounded-Parameter DoS in Rack:QueryParser. (bsc#1242893)
• CVE-2025-32441: Fixed a bug where simultaneous rack requests can restore a deleted rack session. (bsc#1242898)

This update for rmt-server fixes the following issues:

• Update to version 2.23
• CVE-2025-46727: Fixed Unbounded-Parameter DoS in Rack:QueryParser. (bsc#1242893)
• CVE-2025-32441: Fixed a bug where simultaneous rack requests can restore a deleted rack session. (bsc#1242898)

This update for rmt-server fixes the following issues:

• Update to version 2.23
• CVE-2025-46727: Fixed Unbounded-Parameter DoS in Rack:QueryParser. (bsc#1242893)
• CVE-2025-32441: Fixed a bug where simultaneous rack requests can restore a deleted rack session. (bsc#1242898)

This update for rmt-server fixes the following issues:

• Update to version 2.23
• CVE-2025-46727: Fixed Unbounded-Parameter DoS in Rack:QueryParser. (bsc#1242893)
• CVE-2025-32441: Fixed a bug where simultaneous rack requests can restore a deleted rack session. (bsc#1242898)

It was discovered that Rack incorrectly handled deleted rack sessions. An attacker could possibly use this issue to expose sensitive information or to gain unauthorized access to user accounts. (CVE-2025-32441)

It was discovered that Rack incorrectly limited the number of parameters in a web request. An attacker could possibly use this issue to cause a denial of service. This issue only affected Ubuntu 20.04 LTS, Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, Ubuntu 24.10, and Ubuntu 25.04. (CVE-2025-46727)