libssh2 through 1.11.1, fixed in commit 2dae302, contains an out-of-bounds heap read vulnerability in the sftp_symlink() function in src/sftp.c that allows a malicious SSH server or man-in-the-middle attacker to disclose heap memory contents or cause a crash by sending a crafted SSH_FXP_NAME response. Attackers can supply a link_len value larger than the actual packet data in SSH_FXP_NAME responses for SFTP READLINK and REALPATH operations, triggering a heap buffer over-read of up to target_len minus one bytes due to the missing validation of available packet buffer size before the memcpy operation.

The Unity Linux 20 host has a package installed that is affected by a vulnerability as referenced in the UTSA-2026-102704 advisory.

    libssh2 through 1.11.1, fixed in commit 2dae302, contains an out-of-bounds heap read vulnerability in the     sftp_symlink() function in src/sftp.c that allows a malicious SSH server or man-in-the-middle attacker to     disclose heap memory contents or cause a crash by sending a crafted SSH_FXP_NAME response. Attackers can     supply a link_len value larger than the actual packet data in SSH_FXP_NAME responses for SFTP READLINK and     REALPATH operations, triggering a heap buffer over-read of up to target_len minus one bytes due to the     missing validation of available packet buffer size before the memcpy operation.

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

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

The remote host is affected by the vulnerability described in GLSA-202608-17 (libssh2: Multiple Vulnerabilities)

    Multiple vulnerabilities have been discovered in libssh2. Please review the CVE identifiers referenced     below for details.

Tenable has extracted the preceding description block directly from the Gentoo Linux 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 openSUSE 16 host has packages installed that are affected by multiple vulnerabilities as referenced in the openSUSE-SU-2026:21549-1 advisory.

    - CVE-2025-15661: out-of-bounds heap read vulnerability in the `sftp_symlink()` function in `src/sftp.c`     (bsc#1268546).
    - CVE-2026-7598: integer overflow in function `userauth_password` of file `src/userauth.c` (bsc#1263890).
    - CVE-2026-58050: heap buffer overflow due to missing bounds check in attribute count of publickey-     subsystem response       (bsc#1269568).
    - CVE-2026-58051: uninitialized pointer freed when malformed responses are sent by an SSH server     (bsc#1269567).
    - CVE-2026-66032: arbitrary code execution via double-free in SFTP session (bsc#1272737).
    - CVE-2026-66033: denial of service via integer underflow in AES-GCM cipher negotiation (bsc#1272736).
    - CVE-2026-66034: information disclosure and potential arbitrary code execution via heap out-of-bounds     read       (bsc#1272735).
    - CVE-2026-66035: arbitrary code execution via heap buffer overflow during SSH negotiation (bsc#1272734).

Tenable has extracted the preceding description block directly from the SUSE 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 SUSE Linux SLED15 / SLED_SAP15 / SLES15 / SLES_SAP15 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:3541-1 advisory.

    - CVE-2025-15661: out-of-bounds heap read vulnerability in the `sftp_symlink()` function in `src/sftp.c`     (bsc#1268546).
    - CVE-2026-7598: integer overflow in function `userauth_password` of file `src/userauth.c` (bsc#1263890).
    - CVE-2026-58050: heap buffer overflow due to missing bounds check in attribute count of publickey-     subsystem response       (bsc#1269568).
    - CVE-2026-58051: uninitialized pointer freed when malformed responses are sent by an SSH server     (bsc#1269567).
    - CVE-2026-66032: arbitrary code execution via double-free in SFTP session (bsc#1272737).
    - CVE-2026-66033: denial of service via integer underflow in AES-GCM cipher negotiation (bsc#1272736).
    - CVE-2026-66034: information disclosure and potential arbitrary code execution via heap out-of-bounds     read       (bsc#1272735).
    - CVE-2026-66035: arbitrary code execution via heap buffer overflow during SSH negotiation (bsc#1272734).

Tenable has extracted the preceding description block directly from the SUSE 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 SUSE Linux SLES15 / SLES_SAP15 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:3526-1 advisory.

    - CVE-2025-15661: out-of-bounds heap read vulnerability in the `sftp_symlink()` function in `src/sftp.c`     (bsc#1268546).
    - CVE-2026-7598: integer overflow in function `userauth_password` of file `src/userauth.c` (bsc#1263890).
    - CVE-2026-58050: heap buffer overflow due to missing bounds check in attribute count of publickey-     subsystem response       (bsc#1269568).
    - CVE-2026-58051: uninitialized pointer freed when malformed responses are sent by an SSH server     (bsc#1269567).
    - CVE-2026-66032: arbitrary code execution via double-free in SFTP session (bsc#1272737).
    - CVE-2026-66033: denial of service via integer underflow in AES-GCM cipher negotiation (bsc#1272736).
    - CVE-2026-66034: information disclosure and potential arbitrary code execution via heap out-of-bounds     read       (bsc#1272735).
    - CVE-2026-66035: arbitrary code execution via heap buffer overflow during SSH negotiation (bsc#1272734).

Tenable has extracted the preceding description block directly from the SUSE 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 SUSE Linux SLES12 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:3525-1 advisory.

    - CVE-2025-15661: out-of-bounds heap read vulnerability in the `sftp_symlink()` function in `src/sftp.c`     (bsc#1268546).
    - CVE-2026-7598: integer overflow in function `userauth_password` of file `src/userauth.c` (bsc#1263890).
    - CVE-2026-55199: pre-authentication DoS via the `SSH_MSG_EXT_INFO` handler (bsc#1268530).
    - CVE-2026-58050: heap buffer overflow due to missing bounds check in attribute count of publickey-     subsystem response       (bsc#1269568).
    - CVE-2026-58051: uninitialized pointer freed when malformed responses are sent by an SSH server     (bsc#1269567).
    - CVE-2026-66032: arbitrary code execution via double-free in SFTP session (bsc#1272737).
    - CVE-2026-66033: denial of service via integer underflow in AES-GCM cipher negotiation (bsc#1272736).
    - CVE-2026-66034: information disclosure and potential arbitrary code execution via heap out-of-bounds     read       (bsc#1272735).
    - CVE-2026-66035: arbitrary code execution via heap buffer overflow during SSH negotiation (bsc#1272734).

Tenable has extracted the preceding description block directly from the SUSE 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 Fedora 43 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2026-eed9e67393 advisory.

    This update addresses a few security issues, one of which could plausibly result in remote code execution.


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 24.04 LTS / 25.10 / 26.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-8486-1 advisory.

    It was discovered that libssh2 incorrectly handled the sftp_symlink() function. A malicious SSH server or     machine-in-the-middle attacker could possibly use this issue to obtain sensitive information or cause a     denial of service. (CVE-2025-15661)

    It was discovered that libssh2 had a pre-authentication denial of service vulnerability in the     SSH_MSG_EXT_INFO handler. A malicious SSH server could possibly use this issue to cause a client CPU     exhaustion loop, resulting in a denial of service. (CVE-2026-55199)

    It was discovered that libssh2 incorrectly handled packet length fields. A remote attacker could possibly     use this issue to execute arbitrary code. This issue only affected Ubuntu 25.10 and Ubuntu 26.04 LTS.
    (CVE-2026-55200)

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 remote Fedora 44 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2026-ca858b3ed8 advisory.

    This update addresses a few security issues, one of which could plausibly result in remote code execution.


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 Debian 13 host has packages installed that are affected by multiple vulnerabilities as referenced in the dsa-6365 advisory.

    - -------------------------------------------------------------------------     Debian Security Advisory DSA-6365-1                   security@debian.org     https://www.debian.org/security/                       Moritz Muehlenhoff     June 25, 2026                         https://www.debian.org/security/faq
    - -------------------------------------------------------------------------

    Package        : libssh2     CVE ID         : CVE-2025-15661 CVE-2026-7598 CVE-2026-55199 CVE-2026-55200

    Multiple security vulnerabilities were discovered in libssh2, a     client-side C library implementing the SSH2 protocol which could result     in memory disclosure, denial of service or potentially the execution of     arbitrary code.

    For the stable distribution (trixie), these problems have been fixed in     version 1.11.1-1+deb13u1.

    We recommend that you upgrade your libssh2 packages.

    For the detailed security status of libssh2 please refer to     its security tracker page at:
    https://security-tracker.debian.org/tracker/libssh2

    Further information about Debian Security Advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://www.debian.org/security/

    Mailing list: debian-security-announce@lists.debian.org

Tenable has extracted the preceding description block directly from the Debian 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 Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - libssh2 through 1.11.1, fixed in commit 2dae302, contains an out-of-bounds heap read vulnerability in the     sftp_symlink() function in src/sftp.c that allows a malicious SSH server or man-in-the-middle attacker to     disclose heap memory contents or cause a crash by sending a crafted SSH_FXP_NAME response. Attackers can     supply a link_len value larger than the actual packet data in SSH_FXP_NAME responses for SFTP READLINK and     REALPATH operations, triggering a heap buffer over-read of up to target_len minus one bytes due to the     missing validation of available packet buffer size before the memcpy operation. (CVE-2025-15661)

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

ID	Name	Product	Family	Type	Severity
338544	Unity Linux 20.1050e / 20.1060e / 20.1070e Security Update: libssh2 (UTSA-2026-102704)	Nessus	Unity Linux Local Security Checks	Local	high
338224	GLSA-202608-17 : libssh2: Multiple Vulnerabilities	Nessus	Gentoo Local Security Checks	Local	critical
335046	openSUSE 16 Security Update : libssh2_org (openSUSE-SU-2026:21549-1)	Nessus	SuSE Local Security Checks	Local	high
334785	SUSE SLED15 / SLES15 Security Update : libssh2_org (SUSE-SU-2026:3541-1)	Nessus	SuSE Local Security Checks	Local	high
333544	SUSE SLES15 Security Update : libssh2_org (SUSE-SU-2026:3526-1)	Nessus	SuSE Local Security Checks	Local	high
333542	SUSE SLES12 Security Update : libssh2_org (SUSE-SU-2026:3525-1)	Nessus	SuSE Local Security Checks	Local	high
326401	Fedora 43 : libssh2 (2026-eed9e67393)	Nessus	Fedora Local Security Checks	Local	critical
325003	Ubuntu 24.04 LTS / 25.10 / 26.04 LTS : libssh2 vulnerabilities (USN-8486-1)	Nessus	Ubuntu Local Security Checks	Local	critical
323626	Fedora 44 : libssh2 (2026-ca858b3ed8)	Nessus	Fedora Local Security Checks	Local	critical
323060	Debian dsa-6365 : libssh2-1-dev - security update	Nessus	Debian Local Security Checks	Local	critical
321796	Linux Distros Unpatched Vulnerability : CVE-2025-15661	Nessus	Misc.	Local	high

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CVE-2025-15661

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