CVE-2025-8277

The ssh library was designed to be used by programmers needing a working SSH implementation by the mean of a library. The complete control of the client is made by the programmer. With libssh, you can remotely execute programs, transfer files, use a secure and transparent tunnel for your remote programs. With its Secure FTP implementation, you can play with remote files easily, without third-party programs others than libcrypto (from openssl).

Security Fix(es):

A flaw was found in libssh's handling of key exchange (KEX) processes when a client repeatedly sends incorrect KEX guesses. The library fails to free memory during these rekey operations, which can gradually exhaust system memory. This issue can lead to crashes on the client side, particularly when using libgcrypt, which impacts application stability and availability.(CVE-2025-8277)

libssh is a library which implements the SSH protocol. It can be used to implement client and server applications.

Security Fix(es):

• libssh: Double Free Vulnerability in libssh Key Export Functions (CVE-2025-5351)

• libssh: Use of uninitialized variable in privatekey_from_file() (CVE-2025-4878)

• libssh: Write beyond bounds in binary to base64 conversion functions (CVE-2025-4877)

• libssh: NULL Pointer Dereference in libssh KEX Session ID Calculation (CVE-2025-8114)

• libssh: Memory Exhaustion via Repeated Key Exchange in libssh (CVE-2025-8277)

• libssh: Buffer underflow in ssh_get_hexa() on invalid input (CVE-2026-0966)

• libssh: Improper sanitation of paths received from SCP servers (CVE-2026-0964)

• libssh: libssh: Denial of Service via improper configuration file handling (CVE-2026-0965)

• libssh: libssh: Denial of Service via inefficient regular expression processing (CVE-2026-0967)

• libssh: libssh: Denial of Service due to malformed SFTP message (CVE-2026-0968)

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.

Additional Changes:

For detailed information on changes in this release, see the Rocky Linux 9 Release Notes linked from the References section.

A flaw was found in libssh's handling of key exchange (KEX) processes when a client repeatedly sends incorrect KEX guesses. The library fails to free memory during these rekey operations, which can gradually exhaust system memory. This issue can lead to crashes on the client side, particularly when using libgcrypt, which impacts application stability and availability.

libssh is a library which implements the SSH protocol. It can be used to implement client and server applications.

Security Fix(es):

• libssh: Double Free Vulnerability in libssh Key Export Functions (CVE-2025-5351)
• libssh: Use of uninitialized variable in privatekey_from_file() (CVE-2025-4878)
• libssh: Write beyond bounds in binary to base64 conversion functions (CVE-2025-4877)
• libssh: NULL Pointer Dereference in libssh KEX Session ID Calculation (CVE-2025-8114)
• libssh: Memory Exhaustion via Repeated Key Exchange in libssh (CVE-2025-8277)
• libssh: Buffer underflow in ssh_get_hexa() on invalid input (CVE-2026-0966)
• libssh: Improper sanitation of paths received from SCP servers (CVE-2026-0964)
• libssh: libssh: Denial of Service via improper configuration file handling (CVE-2026-0965)
• libssh: libssh: Denial of Service via inefficient regular expression processing (CVE-2026-0967)
• libssh: libssh: Denial of Service due to malformed SFTP message (CVE-2026-0968)

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.

Additional Changes:

For detailed information on changes in this release, see the AlmaLinuxRelease Notes linked from the References section.

A flaw was found in libssh's handling of key exchange (KEX) processes when a client repeatedly sends incorrect KEX guesses. The library fails to free memory during these rekey operations, which can gradually exhaust system memory. This issue can lead to crashes on the client side, particularly when using libgcrypt, which impacts application stability and availability.

A flaw was found in libssh's handling of key exchange (KEX) processes when a client repeatedly sends incorrect KEX guesses. The library fails to free memory during these rekey operations, which can gradually exhaust system memory. This issue can lead to crashes on the client side, particularly when using libgcrypt, which impacts application stability and availability.

• CVE-2025-4877: prevent base64 integer overflow and potential OOB write
• CVE-2025-4878: initialize stack pointers to mitigate use of uninitialized values in legacy privatekey_from_file() path
• CVE-2025-8277: fix DH-GEX packet filter and free unused ephemeral / ECDH keys to prevent memory exhaustion
• CVE-2026-0965: skip non-regular and oversized configuration / known_hosts files to avoid local DoS

• CVE-2025-4877: prevent integer overflow and potential out-of-bounds write in base64 decoder by capping input length to 256MB
• CVE-2025-8277: adjust packet filter to work correctly when DH-GEX is guessed wrongly
• CVE-2026-0965: refuse non-regular and over-sized configuration files in libssh config and known_hosts readers

A flaw was found in libssh's handling of key exchange (KEX) processes when a client repeatedly sends incorrect KEX guesses. The library fails to free memory during these rekey operations, which can gradually exhaust system memory. This issue can lead to crashes on the client side, particularly when using libgcrypt, which impacts application stability and availability.

These are all security issues fixed in the libssh-config-0.11.3-1.1 package on the GA media of openSUSE Tumbleweed.

This update for libssh fixes the following issues:

• Update to version 0.11.4:
• CVE-2026-0964: SCP Protocol Path Traversal in ssh_scp_pull_request() (bsc#1258049)
• CVE-2026-0965: Possible Denial of Service when parsing unexpected configuration files (bsc#1258045)
• CVE-2026-0966: Buffer underflow in ssh_get_hexa() on invalid input (bsc#1258054)
• CVE-2026-0967: Specially crafted patterns could cause DoS (bsc#1258081)
• CVE-2026-0968: OOB Read in sftp_parse_longname() (bsc#1258080)
• CVE-2025-8114: Fix NULL pointer dereference after allocation failure (bsc#1246974)
• CVE-2025-8277: Fix memory leak of ephemeral key pair during repeated wrong KEX (bsc#1249375)

This update for libssh fixes the following issues:

• CVE-2025-8277: memory exhaustion leading to client-side DoS due to improper memory management when KEX process is repeated with incorrect guesses (bsc#1249375).
• CVE-2025-8114: NULL pointer dereference when an allocation error happens during the calculation of the KEX session ID (bsc#1246974).

This update for libssh fixes the following issues:

• CVE-2025-8277: memory exhaustion leading to client-side DoS due to improper memory management when KEX process is repeated with incorrect guesses (bsc#1249375).
• CVE-2025-8114: NULL pointer dereference when an allocation error happens during the calculation of the KEX session ID (bsc#1246974).

This update for libssh fixes the following issues:

• CVE-2025-8114: Fixed NULL pointer dereference when calculating the session ID during the key exchange (KEX) process (bsc#1246974)
• CVE-2025-8277: Fixed Memory Exhaustion via Repeated Key Exchange (bsc#1249375)

This update for libssh fixes the following issues:

• CVE-2025-8114: Fixed NULL pointer dereference when calculating the session ID during the key exchange (KEX) process (bsc#1246974)
• CVE-2025-8277: Fixed Memory Exhaustion via Repeated Key Exchange (bsc#1249375)

This update for libssh fixes the following issues:

• CVE-2025-8277: memory exhaustion leading to client-side DoS due to improper memory management when KEX process is repeated with incorrect guesses (bsc#1249375).
• CVE-2025-8114: NULL pointer dereference when an allocation error happens during the calculation of the KEX session ID (bsc#1246974).

This update for libssh fixes the following issues:

• CVE-2025-8277: memory exhaustion leading to client-side DoS due to improper memory management when KEX process is repeated with incorrect guesses (bsc#1249375).
• CVE-2025-8114: NULL pointer dereference when an allocation error happens during the calculation of the KEX session ID (bsc#1246974).

This update for libssh fixes the following issues:

• CVE-2025-8277: memory exhaustion leading to client-side DoS due to improper memory management when KEX process is repeated with incorrect guesses (bsc#1249375).

This update for libssh fixes the following issues:

• Update to version 0.11.4:
• CVE-2026-0964: SCP Protocol Path Traversal in ssh_scp_pull_request() (bsc#1258049)
• CVE-2026-0965: Possible Denial of Service when parsing unexpected configuration files (bsc#1258045)
• CVE-2026-0966: Buffer underflow in ssh_get_hexa() on invalid input (bsc#1258054)
• CVE-2026-0967: Specially crafted patterns could cause DoS (bsc#1258081)
• CVE-2026-0968: OOB Read in sftp_parse_longname() (bsc#1258080)
• CVE-2025-8114: Fix NULL pointer dereference after allocation failure (bsc#1246974)
• CVE-2025-8277: Fix memory leak of ephemeral key pair during repeated wrong KEX (bsc#1249375)

This update for libssh fixes the following issues:

• Update to version 0.11.4:
• CVE-2026-0964: SCP Protocol Path Traversal in ssh_scp_pull_request() (bsc#1258049)
• CVE-2026-0965: Possible Denial of Service when parsing unexpected configuration files (bsc#1258045)
• CVE-2026-0966: Buffer underflow in ssh_get_hexa() on invalid input (bsc#1258054)
• CVE-2026-0967: Specially crafted patterns could cause DoS (bsc#1258081)
• CVE-2026-0968: OOB Read in sftp_parse_longname() (bsc#1258080)
• CVE-2025-8114: Fix NULL pointer dereference after allocation failure (bsc#1246974)
• CVE-2025-8277: Fix memory leak of ephemeral key pair during repeated wrong KEX (bsc#1249375)

It was discovered that libssh clients incorrectly handled the key exchange process. A remote attacker could possibly use this issue to cause libssh clients to crash, resulting in a denial of service. (CVE-2025-8277)

It was discovered that the libssh SCP client incorrectly sanitized paths received from servers. A remote attacker could use this issue to cause libssh SCP clients to overwrite files outside of the working directory and possibly execute arbitrary code. (CVE-2026-0964)

It was discovered that libssh incorrectly handled parsing configuration files. A local attacker could possibly use this issue to cause libssh to access non-regular files, resulting in a denial of service. (CVE-2026-0965)

It was discovered that libssh incorrectly handled the ssh_get_hexa() function. A remote attacker could possibly use this issue to cause libssh to crash, resulting in a denial of service. (CVE-2026-0966)

It was discovered that libssh incorrectly handled certain regular expressions. A local attacker could possibly use this issue to cause libssh to consume resources, resulting in a denial of service. (CVE-2026-0967)

It was discovered that the libssh SFTP client incorrectly handled certain malformed longname fields. A remote attacker could use this issue to cause libssh SFTP clients to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2026-0968)

USN-8051-1 fixed vulnerabilities in libssh. This update provides the corresponding updates for Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, and Ubuntu 20.04 LTS.

Original advisory details:

It was discovered that libssh clients incorrectly handled the key exchange process. A remote attacker could possibly use this issue to cause libssh clients to crash, resulting in a denial of service. (CVE-2025-8277)

It was discovered that the libssh SCP client incorrectly sanitized paths received from servers. A remote attacker could use this issue to cause libssh SCP clients to overwrite files outside of the working directory and possibly execute arbitrary code. (CVE-2026-0964)

It was discovered that libssh incorrectly handled parsing configuration files. A local attacker could possibly use this issue to cause libssh to access non-regular files, resulting in a denial of service. (CVE-2026-0965)

It was discovered that libssh incorrectly handled the ssh_get_hexa() function. A remote attacker could possibly use this issue to cause libssh to crash, resulting in a denial of service. (CVE-2026-0966)

It was discovered that libssh incorrectly handled certain regular expressions. A local attacker could possibly use this issue to cause libssh to consume resources, resulting in a denial of service. (CVE-2026-0967)

It was discovered that the libssh SFTP client incorrectly handled certain malformed longname fields. A remote attacker could use this issue to cause libssh SFTP clients to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2026-0968)