A flaw was found in the SFTP server message decoding logic of libssh. The issue occurs due to an incorrect packet length check that allows an integer overflow when handling large payload sizes on 32-bit systems. This issue leads to failed memory allocation and causes the server process to crash, resulting in a denial of service.

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 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.

There are packages installed that are affected by multiple vulnerabilities referenced in the following CVEs:

  - 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)

  - 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 libssh library in versions less than 0.11.2. An out-of-bounds read can be
    triggered in the sftp_handle function due to an incorrect comparison check that permits the function to
    access memory beyond the valid handle list and to return an invalid pointer, which is used in further
    processing. This vulnerability allows an authenticated remote attacker to potentially read unintended
    memory regions, exposing sensitive information or affect service behavior. (CVE-2025-5318)

  - 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)

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	Type	Severity
244363	Fedora 41 : libssh (2025-18e8506d3a)	Nessus	Fedora Local Security Checks	Local	medium
241506	Ubuntu 22.04 LTS / 24.04 LTS / 24.10 / 25.04 : libssh vulnerabilities (USN-7619-1)	Nessus	Ubuntu Local Security Checks	Local	medium
427911	Alpine: multiple libssh packages: security update to 0.11.2-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	Local	high
427911	Alpine: multiple libssh packages: security update to 0.11.2-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	Local	high
240488	Slackware Linux 15.0 / current libssh Multiple Vulnerabilities (SSA:2025-175-01)	Nessus	Slackware Local Security Checks	Local	medium

Detections

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CVE-2025-5449

medium

Tenable Plugins

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medium