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.

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2025-1155 advisory.

    The privatekey_from_file() uses an uninitialized variable under certainconditions, such as if the file     specified by the filename argument doesn'texist. This causes the code to return an invalid private key.

    This defect, in turn, might cause signing failure. The bug might also cause aUse-After-Free or corrupt the     heap.

    Note that privatekey_from_file() is a deprecated function and shouldn't be usedanymore! (CVE-2025-4878)

    An incorrect comparison check allows to read beyond bounds in the sftp_handle() in the sftp server     implementation. Thus an invalid pointer is returned as the handle and we try to continue using that.
    (CVE-2025-5318)

    pki_key_to_blob() can cause a double free on certain errors when using OpenSSL>= 3.0.  The function is     used by different other functions which allow toexport public or private keys to blobs or base64.

    The function is using the variable params without resetting it to NULL afterfree.  In case of low-memory     conditions when the allocation of string fails,the libssh calls the OSSL_PARAM_free() with the same     arguments, which willlikely crash. (CVE-2025-5351)

    If there is an error in initializing ChaCha20 cipher with OpenSSL, an invaliderror code is returned. This     can happen if there is an heap exhaustion.  Thiserror is not correctly detected and could allow libssh to     use partiallyinitialized cipher context.

    This is caused by the mismatch of return value meaning from OpenSSL and libssh,where OpenSSL error (rv=0)     aliases with SSH_OK (0) and is returned directlyfrom the function chacha20_poly1305_set_key(). This will     likely cause errorsomewhere down the road. (CVE-2025-5987)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

An update of the libssh package has been released.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch 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.
    (CVE-2025-5351)

Note that Nessus relies on the presence of the package as reported by the vendor.

The remote Fedora 41 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2025-18e8506d3a advisory.

    New upstream release with security fixes for CVE-2025-4877, CVE-2025-4878, CVE-2025-5987, CVE-2025-5318,     CVE-2025-5351, CVE-2025-5372, CVE-2025-5449

    ----

    Automatic update for libssh-0.11.0-1.fc41.


Tenable has extracted the preceding description block directly from the Fedora security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The version of libssh installed on the remote CBL Mariner 2.0 host is prior to tested version. It is, therefore, affected by a vulnerability as referenced in the CVE-2025-5351 advisory.

  - 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)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The version of libssh installed on the remote Azure Linux 3.0 host is prior to tested version. It is, therefore, affected by a vulnerability as referenced in the CVE-2025-5351 advisory.

  - 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)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote Ubuntu 22.04 LTS / 24.04 LTS / 24.10 / 25.04 host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-7619-1 advisory.

    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)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The version of libssh installed on the remote host is prior to 0.11.2. It is, therefore, affected by multiple vulnerabilities as referenced in the SSA:2025-175-01 advisory.

    New libssh packages are available for Slackware 15.0 and -current to fix security issues.

Tenable has extracted the preceding description block directly from the libssh security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Severity
261738	Amazon Linux 2023 : libssh, libssh-config, libssh-devel (ALAS2023-2025-1155)	Nessus	Amazon Linux Local Security Checks	high
260441	Photon OS 5.0: Libssh PHSA-2025-5.0-0597	Nessus	PhotonOS Local Security Checks	high
258011	Linux Distros Unpatched Vulnerability : CVE-2025-5351	Nessus	Misc.	medium
244363	Fedora 41 : libssh (2025-18e8506d3a)	Nessus	Fedora Local Security Checks	medium
242392	CBL Mariner 2.0 Security Update: libssh (CVE-2025-5351)	Nessus	MarinerOS Local Security Checks	medium
242385	Azure Linux 3.0 Security Update: libssh (CVE-2025-5351)	Nessus	Azure Linux Local Security Checks	medium
241506	Ubuntu 22.04 LTS / 24.04 LTS / 24.10 / 25.04 : libssh vulnerabilities (USN-7619-1)	Nessus	Ubuntu Local Security Checks	medium
240488	Slackware Linux 15.0 / current libssh Multiple Vulnerabilities (SSA:2025-175-01)	Nessus	Slackware Local Security Checks	medium

Detections

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CVE-2025-5351

medium

Tenable Plugins

high

high

medium

medium

medium

medium

medium

medium