CVE-2025-5351

A flaw was found in the key export functionality of libssh. The issue occurs in the internal function responsible for converting cryptographic keys into serialized formats. During error handling, a memory structure is freed but not cleared, leading to a potential double free issue if an additional failure occurs later in the function. This condition may result in heap corruption or application instability in low-memory scenarios, posing a risk to system reliability where key export operations are performed.

A flaw was found in the key export functionality of libssh. The issue occurs in the internal function responsible for converting cryptographic keys into serialized formats. During error handling, a memory structure is freed but not cleared, leading to a potential double free issue if an additional failure occurs later in the function. This condition may result in heap corruption or application instability in low-memory scenarios, posing a risk to system reliability where key export operations are performed.

A flaw was found in the key export functionality of libssh. The issue occurs in the internal function responsible for converting cryptographic keys into serialized formats. During error handling, a memory structure is freed but not cleared, leading to a potential double free issue if an additional failure occurs later in the function. This condition may result in heap corruption or application instability in low-memory scenarios, posing a risk to system reliability where key export operations are performed.

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 vulnerability classified as critical was found in libssh up to 0.11.1.The CWE definition for the vulnerability is CWE-119. The product performs operations on a memory buffer, but it can read from or write to a memory location that is outside of the intended boundary of the buffer.As an impact it is known to affect confidentiality, integrity, and availability.Upgrading to version 0.11.2 eliminates this vulnerability.(CVE-2025-4877)

A vulnerability, which was classified as problematic, has been found in libssh up to 0.11.1.Using CWE to declare the problem leads to CWE-824. The product accesses or uses a pointer that has not been initialized.Impacted is confidentiality, integrity, and availability.Upgrading to version 0.11.2 eliminates this vulnerability.(CVE-2025-4878)

A flaw was found in the key export functionality of libssh. The issue occurs in the internal function responsible for converting cryptographic keys into serialized formats. During error handling, a memory structure is freed but not cleared, leading to a potential double free issue if an additional failure occurs later in the function. This condition may result in heap corruption or application instability in low-memory scenarios, posing a risk to system reliability where key export operations are performed.(CVE-2025-5351)

A flaw was found in libssh versions built with OpenSSL versions older than 3.0, specifically in the ssh_kdf() function responsible for key derivation. Due to inconsistent interpretation of return values where OpenSSL uses 0 to indicate failure and libssh uses 0 for success—the function may mistakenly return a success status even when key derivation fails. This results in uninitialized cryptographic key buffers being used in subsequent communication, potentially compromising SSH sessions' confidentiality, integrity, and availability.(CVE-2025-5372)

A flaw was found in libssh when using the ChaCha20 cipher with the OpenSSL library. If an attacker manages to exhaust the heap space, this error is not detected and may lead to libssh using a partially initialized cipher context. This occurs because the OpenSSL error code returned aliases with the SSH_OK code, resulting in libssh not properly detecting the error returned by the OpenSSL library. This issue can lead to undefined behavior, including compromised data confidentiality and integrity or crashes.(CVE-2025-5987)

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 vulnerability classified as critical was found in libssh up to 0.11.1.The CWE definition for the vulnerability is CWE-119. The product performs operations on a memory buffer, but it can read from or write to a memory location that is outside of the intended boundary of the buffer.As an impact it is known to affect confidentiality, integrity, and availability.Upgrading to version 0.11.2 eliminates this vulnerability.(CVE-2025-4877)

A vulnerability, which was classified as problematic, has been found in libssh up to 0.11.1.Using CWE to declare the problem leads to CWE-824. The product accesses or uses a pointer that has not been initialized.Impacted is confidentiality, integrity, and availability.Upgrading to version 0.11.2 eliminates this vulnerability.(CVE-2025-4878)

A flaw was found in the key export functionality of libssh. The issue occurs in the internal function responsible for converting cryptographic keys into serialized formats. During error handling, a memory structure is freed but not cleared, leading to a potential double free issue if an additional failure occurs later in the function. This condition may result in heap corruption or application instability in low-memory scenarios, posing a risk to system reliability where key export operations are performed.(CVE-2025-5351)

A flaw was found in libssh versions built with OpenSSL versions older than 3.0, specifically in the ssh_kdf() function responsible for key derivation. Due to inconsistent interpretation of return values where OpenSSL uses 0 to indicate failure and libssh uses 0 for success—the function may mistakenly return a success status even when key derivation fails. This results in uninitialized cryptographic key buffers being used in subsequent communication, potentially compromising SSH sessions' confidentiality, integrity, and availability.(CVE-2025-5372)

A flaw was found in libssh when using the ChaCha20 cipher with the OpenSSL library. If an attacker manages to exhaust the heap space, this error is not detected and may lead to libssh using a partially initialized cipher context. This occurs because the OpenSSL error code returned aliases with the SSH_OK code, resulting in libssh not properly detecting the error returned by the OpenSSL library. This issue can lead to undefined behavior, including compromised data confidentiality and integrity or crashes.(CVE-2025-5987)

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):

There's a vulnerability in the libssh package where when a libssh consumer passes in an unexpectedly large input buffer to ssh_get_fingerprint_hash() function. In such cases the bin_to_base64() function can experience an integer overflow leading to a memory under allocation, when that happens it's possible that the program perform out of bounds write leading to a heap corruption. This issue affects only 32-bits builds of libssh.(CVE-2025-4877)

A vulnerability was found in libssh, where an uninitialized variable exists under certain conditions in the privatekey_from_file() function. This flaw can be triggered if the file specified by the filename doesn't exist and may lead to possible signing failures or heap corruption.(CVE-2025-4878)

A flaw was found in the key export functionality of libssh. The issue occurs in the internal function responsible for converting cryptographic keys into serialized formats. During error handling, a memory structure is freed but not cleared, leading to a potential double free issue if an additional failure occurs later in the function. This condition may result in heap corruption or application instability in low-memory scenarios, posing a risk to system reliability where key export operations are performed.(CVE-2025-5351)

A flaw was found in libssh versions built with OpenSSL versions older than 3.0, specifically in the ssh_kdf() function responsible for key derivation. Due to inconsistent interpretation of return values where OpenSSL uses 0 to indicate failure and libssh uses 0 for success—the function may mistakenly return a success status even when key derivation fails. This results in uninitialized cryptographic key buffers being used in subsequent communication, potentially compromising SSH sessions' confidentiality, integrity, and availability.(CVE-2025-5372)

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.

Root has patched CVE-2025-5351 in the libssh package for Root:Debian:12. Multiple fixed versions available.

A flaw was found in the key export functionality of libssh. The issue occurs in the internal function responsible for converting cryptographic keys into serialized formats. During error handling, a memory structure is freed but not cleared, leading to a potential double free issue if an additional failure occurs later in the function. This condition may result in heap corruption or application instability in low-memory scenarios, posing a risk to system reliability where key export operations are performed.

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 the key export functionality of libssh. The issue occurs in the internal function responsible for converting cryptographic keys into serialized formats. During error handling, a memory structure is freed but not cleared, leading to a potential double free issue if an additional failure occurs later in the function. This condition may result in heap corruption or application instability in low-memory scenarios, posing a risk to system reliability where key export operations are performed.

A flaw was found in the key export functionality of libssh. The issue occurs in the internal function responsible for converting cryptographic keys into serialized formats. During error handling, a memory structure is freed but not cleared, leading to a potential double free issue if an additional failure occurs later in the function. This condition may result in heap corruption or application instability in low-memory scenarios, posing a risk to system reliability where key export operations are performed.

• CVE-2025-5351: fix double-free conditions
• CVE-2025-8114: fix NULL pointer dereference

CVE-2025-4877 Write beyond bounds in binary to base64 conversion functions CVE-2025-4878 Use of uninitialized variable in privatekey_from_file() CVE-2025-5318 Likely read beyond bounds in sftp server handle management CVE-2025-5351 Double free in functions exporting keys CVE-2025-5372 ssh_kdf() returns a success code on certain failures CVE-2025-5449 Likely read beyond bounds in sftp server message decoding CVE-2025-5987 Invalid return code for chacha20 poly1305 with OpenSSL backend

These are all security issues fixed in the libssh-config-0.11.2-1.1 package on the GA media of openSUSE Tumbleweed.

This update for libssh fixes the following issues:

• CVE-2025-5372: ssh_kdf() returns a success code on certain failures (bsc#1245314)
• CVE-2025-5987: Invalid return code for chacha20 poly1305 with OpenSSL backend (bsc#1245317)
• CVE-2025-4877: Write beyond bounds in binary to base64 conversion functions (bsc#1245309)
• CVE-2025-4878: Use of uninitialized variable in privatekey_from_file() (bsc#1245310)
• CVE-2025-5318: Likely read beyond bounds in sftp server handle management (bsc#1245311)
• CVE-2025-5351: Double free in functions exporting keys (bsc#1245312)

This update for libssh fixes the following issues:

• CVE-2025-5372: ssh_kdf() returns a success code on certain failures (bsc#1245314)
• CVE-2025-5987: Invalid return code for chacha20 poly1305 with OpenSSL backend (bsc#1245317)
• CVE-2025-4877: Write beyond bounds in binary to base64 conversion functions (bsc#1245309)
• CVE-2025-4878: Use of uninitialized variable in privatekey_from_file() (bsc#1245310)
• CVE-2025-5318: Likely read beyond bounds in sftp server handle management (bsc#1245311)
• CVE-2025-5351: Double free in functions exporting keys (bsc#1245312)

Ronald Crane discovered that libssh incorrectly handled certain base64 conversions. An attacker could use this issue to cause libssh to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2025-4877)

Ronald Crane discovered that libssh incorrectly handled the privatekey_from_file() function. An attacker could use this issue to cause libssh to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2025-4878)

Ronald Crane discovered that libssh incorrectly handled certain memory operations in the sftp server. An attacker could possibly use this issue to cause libssh to crash, resulting in a denial of service. (CVE-2025-5318, CVE-2025-5449)

Ronald Crane discovered that libssh incorrectly handled exporting keys. An attacker could possibly use this issue to cause libssh to crash, resulting in a denial of service. This issue only affected Ubuntu 24.04 LTS, Ubuntu 24.10, and Ubuntu 25.04. (CVE-2025-5351)

Ronald Crane discovered that libssh incorrectly handled the ssh_kdf() function. An attacker could use this issue to cause libssh to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2025-5372)

Ronald Crane discovered that libssh incorrectly handled the ChaCha20 cipher. An attacker could possibly use this issue to cause libssh to use partially initialized cypher content. This issue only affected Ubuntu 24.04 LTS, Ubuntu 24.10, and Ubuntu 25.04. (CVE-2025-5987)