CVE-2026-3731

A weakness has been identified in libssh up to 0.11.3. The impacted element is the function sftp_extensions_get_name/sftp_extensions_get_data of the file src/sftp.c of the component SFTP Extension Name Handler. Executing a manipulation of the argument idx can lead to out-of-bounds read. The attack may be performed from remote. Upgrading to version 0.11.4 and 0.12.0 is sufficient to resolve this issue. This patch is called 855a0853ad3abd4a6cd85ce06fce6d8d4c7a0b60. You should upgrade the affected component.

A weakness has been identified in libssh up to 0.11.3. The impacted element is the function sftp_extensions_get_name/sftp_extensions_get_data of the file src/sftp.c of the component SFTP Extension Name Handler. Executing a manipulation of the argument idx can lead to out-of-bounds read. The attack may be performed from remote. Upgrading to version 0.11.4 and 0.12.0 is sufficient to resolve this issue. This patch is called 855a0853ad3abd4a6cd85ce06fce6d8d4c7a0b60. You should upgrade the affected component.

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):

(CVE-2026-0964)

(CVE-2026-0965)

(CVE-2026-0966)

(CVE-2026-0967)

(CVE-2026-0968)

A weakness has been identified in libssh up to 0.11.3. The impacted element is the function sftp_extensions_get_name/sftp_extensions_get_data of the file src/sftp.c of the component SFTP Extension Name Handler. Executing a manipulation of the argument idx can lead to out-of-bounds read. The attack may be performed from remote. Upgrading to version 0.11.4 and 0.12.0 is sufficient to resolve this issue. This patch is called 855a0853ad3abd4a6cd85ce06fce6d8d4c7a0b60. You should upgrade the affected component.(CVE-2026-3731)

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 weakness has been identified in libssh up to 0.11.3. The impacted element is the function sftp_extensions_get_name/sftp_extensions_get_data of the file src/sftp.c of the component SFTP Extension Name Handler. Executing a manipulation of the argument idx can lead to out-of-bounds read. The attack may be performed from remote. Upgrading to version 0.11.4 and 0.12.0 is sufficient to resolve this issue. This patch is called 855a0853ad3abd4a6cd85ce06fce6d8d4c7a0b60. You should upgrade the affected component.(CVE-2026-3731)

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 weakness has been identified in libssh up to 0.11.3. The impacted element is the function sftp_extensions_get_name/sftp_extensions_get_data of the file src/sftp.c of the component SFTP Extension Name Handler. Executing a manipulation of the argument idx can lead to out-of-bounds read. The attack may be performed from remote. Upgrading to version 0.11.4 and 0.12.0 is sufficient to resolve this issue. This patch is called 855a0853ad3abd4a6cd85ce06fce6d8d4c7a0b60. You should upgrade the affected component.(CVE-2026-3731)

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 weakness has been identified in libssh up to 0.11.3. The impacted element is the function sftp_extensions_get_name/sftp_extensions_get_data of the file src/sftp.c of the component SFTP Extension Name Handler. Executing a manipulation of the argument idx can lead to out-of-bounds read. The attack may be performed from remote. Upgrading to version 0.11.4 and 0.12.0 is sufficient to resolve this issue. This patch is called 855a0853ad3abd4a6cd85ce06fce6d8d4c7a0b60. You should upgrade the affected component.(CVE-2026-3731)

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 weakness has been identified in libssh up to 0.11.3. The impacted element is the function sftp_extensions_get_name/sftp_extensions_get_data of the file src/sftp.c of the component SFTP Extension Name Handler. Executing a manipulation of the argument idx can lead to out-of-bounds read. The attack may be performed from remote. Upgrading to version 0.11.4 and 0.12.0 is sufficient to resolve this issue. This patch is called 855a0853ad3abd4a6cd85ce06fce6d8d4c7a0b60. You should upgrade the affected component.(CVE-2026-3731)

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 weakness has been identified in libssh up to 0.11.3. The impacted element is the function sftp_extensions_get_name/sftp_extensions_get_data of the file src/sftp.c of the component SFTP Extension Name Handler. Executing a manipulation of the argument idx can lead to out-of-bounds read. The attack may be performed from remote. Upgrading to version 0.11.4 and 0.12.0 is sufficient to resolve this issue. This patch is called 855a0853ad3abd4a6cd85ce06fce6d8d4c7a0b60. You should upgrade the affected component.(CVE-2026-3731)

Root has patched CVE-2026-3731 in the rootio-libssh package for Root:Ubuntu:24.04. Multiple fixed versions available.

A weakness has been identified in libssh up to 0.11.3. The impacted element is the function sftp_extensions_get_name/sftp_extensions_get_data of the file src/sftp.c of the component SFTP Extension Name Handler. Executing a manipulation of the argument idx can lead to out-of-bounds read. The attack may be performed from remote. Upgrading to version 0.11.4 and 0.12.0 is sufficient to resolve this issue. This patch is called 855a0853ad3abd4a6cd85ce06fce6d8d4c7a0b60. You should upgrade the affected component.

A weakness has been identified in libssh up to 0.11.3. The impacted element is the function sftp_extensions_get_name/sftp_extensions_get_data of the file src/sftp.c of the component SFTP Extension Name Handler. Executing a manipulation of the argument idx can lead to out-of-bounds read. The attack may be performed from remote. Upgrading to version 0.11.4 and 0.12.0 is sufficient to resolve this issue. This patch is called 855a0853ad3abd4a6cd85ce06fce6d8d4c7a0b60. You should upgrade the affected component.

A weakness has been identified in libssh up to 0.11.3. The impacted element is the function sftp_extensions_get_name/sftp_extensions_get_data of the file src/sftp.c of the component SFTP Extension Name Handler. Executing a manipulation of the argument idx can lead to out-of-bounds read. The attack may be performed from remote. Upgrading to version 0.11.4 and 0.12.0 is sufficient to resolve this issue. This patch is called 855a0853ad3abd4a6cd85ce06fce6d8d4c7a0b60. You should upgrade the affected component.

• CVE-2026-3731: fix out-of-bounds read in sftp_extensions_get_name and sftp_extensions_get_data when idx equals the extension count

• SECURITY UPDATE: remote out-of-bounds read in SFTP extension name handler
  • debian/patches/CVE-2026-3731.patch: Fix out-of-bound read from sftp extensions; correct index comparison from '>' to '>=' and prevent access past extension count.
  • CVE-2026-3731

• SECURITY UPDATE: out-of-bounds read from manipulated SFTP extension index
  • debian/patches/CVE-2026-3731.patch: Fix out-of-bound read in sftp extensions by replacing '>' with '>=' in index checks; cause: off-by-one error in index comparison allowing idx equal count.
  • CVE-2026-3731

• CVE-2026-3731: fix off-by-one in sftp_extensions_get_name/sftp_extensions_get_data

• CVE-2026-3731: fix off-by-one in sftp_extensions_get_name/sftp_extensions_get_data

• Fix CVE-2026-3731: out-of-bounds read in SFTP extension name handler

• CVE-2026-3731: Validate idx and add bounds checks; prevent out-of-bounds read in SFTP Extension Name Handler via manipulated idx.

• SECURITY UPDATE: out-of-bounds read in sftp extension name handler
  • debian/patches/CVE-2026-3731.patch: fix off-by-one bounds check in sftp_extensions_get_name and sftp_extensions_get_data
  • CVE-2026-3731

This update for libssh fixes the following issues:

• CVE-2026-3731: Denial of Service via out-of-bounds read in SFTP extension name handler (bsc#1259377).

This update for libssh fixes the following issues:

• CVE-2026-3731: Denial of Service via out-of-bounds read in SFTP extension name handler (bsc#1259377).

This update for libssh fixes the following issues:

• CVE-2026-3731: denial of service via out-of-bounds read in SFTP extension name handler (bsc#1259377).
• 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 a denial of service (bsc#1258081).
• CVE-2026-0968: out-of-bounds read in sftp_parse_longname() (bsc#1258080).

This update for libssh fixes the following issues:

• CVE-2026-0964: improper sanitation of paths received from SCP servers can cause path traversal (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 denial of service (bsc#1258081).
• CVE-2026-0968: malformed SFTP message can lead to out of bound read (bsc#1258080).
• CVE-2026-3731: denial of service via out-of-bounds read in SFTP extension name handler (bsc#1259377).

This update for libssh fixes the following issue:

• CVE-2026-3731: Denial of Service via out-of-bounds read in SFTP extension name handler (bsc#1259377).

This update for libssh fixes the following issues:

• CVE-2026-3731: denial of Service via out-of-bounds read in SFTP extension name handler (bsc#1259377).
• CVE-2026-59843: denial of service via zero advertised channel packet size (bsc#1272164).
• CVE-2026-59844: denial of service via oversized SFTP read length (bsc#1272165).
• CVE-2026-59845: denial of service via unchecked ProxyCommand fork() failure (bsc#1272166).
• CVE-2026-59846: information disclosure via ProxyCommand %r username expansion (bsc#1272167).
• CVE-2026-59847: integrity downgrade via OpenSSL AES-GCM tag verification (bsc#1272168).
• CVE-2026-59848: denial of service via SFTP responses with unknown request IDs (bsc#1272169).
• CVE-2026-59850: use-after-free via data callbacks on closed channels (bsc#1272171).

This update for libssh fixes the following issues

• CVE-2026-3731: denial of service via out-of-bounds read in SFTP extension name handler (bsc#1259377).
• CVE-2026-59843: denial of service via zero advertised channel packet size (bsc#1272164).
• CVE-2026-59844: denial of service via oversized SFTP read length (bsc#1272165).
• CVE-2026-59845: denial of service via unchecked ProxyCommand fork() failure (bsc#1272166).
• CVE-2026-59846: information disclosure via ProxyCommand %r username expansion (bsc#1272167).
• CVE-2026-59847: integrity downgrade via OpenSSL AES-GCM tag verification (bsc#1272168).
• CVE-2026-59848: denial of service via SFTP responses with unknown request IDs (bsc#1272169).
• CVE-2026-59850: use-after-free via data callbacks on closed channels (bsc#1272171).

It was discovered that libssh incorrectly performed bounds checking when processing SFTP extensions. If a client application queried extension data out of bounds, it could cause the application to crash, resulting in a denial of service, or exhibit unintended behavior.

USN-8093-1 fixed a vulnerability in libssh. This update provides the corresponsing fix for Ubuntu 26.04 LTS.

Original advisory details:

It was discovered that libssh incorrectly performed bounds checking when processing SFTP extensions. If a client application queried extension data out of bounds, it could cause the application to crash, resulting in a denial of service, or exhibit unintended behavior.