libssh2 through 1.11.1, fixed in commit a13bb6c, contains a missing bounds check vulnerability that allows a malicious SSH server to trigger an arbitrary-length heap out-of-bounds read and a free of an uninitialized pointer via the publickey subsystem. In libssh2_publickey_list_fetch(), the version 1 response parser reads a server-controlled comment_len value and advances the parse pointer without verifying sufficient bytes remain in the buffer, causing the out-of-bounds read to leak heap pointers from adjacent allocations defeating ASLR, followed by heap allocator state corruption when the error cleanup path frees an uninitialized pointer from a non-zeroed realloc() region.

The remote Debian 12 host has packages installed that are affected by multiple vulnerabilities as referenced in the dla-4773 advisory.

    -------------------------------------------------------------------------     Debian LTS Advisory DLA-4773-1                debian-lts@lists.debian.org     https://www.debian.org/lts/security/                       Emmanuel Arias     September 05, 2026                            https://wiki.debian.org/LTS
    -------------------------------------------------------------------------

    Package        : libssh2     Version        : 1.10.0-3+deb12u1     CVE ID         : CVE-2025-15661 CVE-2026-7598 CVE-2026-58050 CVE-2026-58051                      CVE-2026-66032 CVE-2026-66034     Debian Bug     : 1140401 1142856 1144415

    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.

    CVE-2025-15661

        A malicious server could send an oversized link_len in SSH_FXP_NAME         responses (READLINK/REALPATH) and trigger an out-of-bounds memcpy, leaking         heap memory or crashing the client

    CVE-2026-7598

        The impacted element is the function userauth_password of the file         src/userauth.c. Such manipulation of the argument

    CVE-2026-58050

        libsshw2 reads an attacker-controlled 32-bit attribute without bounds         checking, so on 32-bit platforms the multiplication overflows to an         undersized buffer. count from a publickey-subsystem response and uses it         without bounds checking, causing an overflows to an undersized buffer

    CVE-2026-58051

        libssh2 grows its publickey list with SSH2_REALLOC but does not         zero-initialize new entries before parsing populates them, so a parse         failure reaching the cleanup path leaves. A malicious SSH server offering         the publickey subsystem can use a malformed response to make cleanup free an         uninitialized, attacker-influenceable attrs pointer in a connecting libssh2         client.

    CVE-2026-66032

        Fix double free in sftp_open() reachable from a malicious server during SFTP         session setup (SSH_FXP_OPEN answered with SSH_FXP_STATUS/FX_OK followed by a         failing sftp_packet_require()) (Closes:

    CVE-2026-66034

        Fix missing bounds check in libssh2_publickey_list_fetch() leading to a heap         out-of-bounds read and a free of an uninitialized pointer, triggerable by a         malicious server via the publickey subsystem.


    For Debian 12 bookworm, these problems have been fixed in version     1.10.0-3+deb12u1.

    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 LTS security advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://wiki.debian.org/LTS     Attachment:
    signature.asc     Description: PGP signature

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 remote Redhat Enterprise Linux 7 host has packages installed that are affected by multiple vulnerabilities as referenced in the RHSA-2026:61752 advisory.

    The libssh2 packages provide a library that implements the SSH2 protocol.

    Security Fix(es):

    * libssh2: integer overflow via large username or password arguments (CVE-2026-7598)

    * libssh2: libssh2: Heap buffer overflow via integer overflow in publickey attribute allocation     (CVE-2026-58050)

    * libssh2: libssh2: Arbitrary code execution via double-free in SFTP session (CVE-2026-66032)

    * libssh2: libssh2: Information disclosure and potential arbitrary code execution via heap out-of-bounds     read (CVE-2026-66034)

    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.

Tenable has extracted the preceding description block directly from the Red Hat Enterprise 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 Unity Linux 20 host has a package installed that is affected by a vulnerability as referenced in the UTSA-2026-102688 advisory.

    libssh2 through 1.11.1, fixed in commit a13bb6c, contains a missing bounds check vulnerability that allows     a malicious SSH server to trigger an arbitrary-length heap out-of-bounds read and a free of an     uninitialized pointer via the publickey subsystem. In libssh2_publickey_list_fetch(), the version 1     response parser reads a server-controlled comment_len value and advances the parse pointer without     verifying sufficient bytes remain in the buffer, causing the out-of-bounds read to leak heap pointers from     adjacent allocations defeating ASLR, followed by heap allocator state corruption when the error cleanup     path frees an uninitialized pointer from a non-zeroed realloc() region.

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 version of libssh2 installed on the remote host is prior to 1.4.3-12. It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2-2026-3861 advisory.

    libssh2 through 1.11.1, fixed in commit 5e47761, contains a double-free vulnerability in the sftp_open()     function in src/sftp.c that allows a malicious SSH server to corrupt the heap of any authenticated client     opening an SFTP session. When a server responds to SSH_FXP_OPEN with SSH_FXP_STATUS containing FX_OK, the     response data buffer is freed, and if a subsequent sftp_packet_require() call returns a specific error     such as LIBSSH2_ERROR_CHANNEL_PACKET_EXCEEDED, the same pointer is freed a second time, enabling tcache     dup conditions on glibc systems that allow overlapping allocations and function pointer overwrites.
    (CVE-2026-66032)

    libssh2 through 1.11.1, fixed in commit a13bb6c, contains a missing bounds check vulnerability that allows     a malicious SSH server to trigger an arbitrary-length heap out-of-bounds read and a free of an     uninitialized pointer via the publickey subsystem. In libssh2_publickey_list_fetch(), the version 1     response parser reads a server-controlled comment_len value and advances the parse pointer without     verifying sufficient bytes remain in the buffer, causing the out-of-bounds read to leak heap pointers from     adjacent allocations defeating ASLR, followed by heap allocator state corruption when the error cleanup     path frees an uninitialized pointer from a non-zeroed realloc() region. (CVE-2026-66034)

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.

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-2056 advisory.

    libssh2 through 1.11.1, fixed in commit 5e47761, contains a double-free vulnerability in the sftp_open()     function in src/sftp.c that allows a malicious SSH server to corrupt the heap of any authenticated client     opening an SFTP session. When a server responds to SSH_FXP_OPEN with SSH_FXP_STATUS containing FX_OK, the     response data buffer is freed, and if a subsequent sftp_packet_require() call returns a specific error     such as LIBSSH2_ERROR_CHANNEL_PACKET_EXCEEDED, the same pointer is freed a second time, enabling tcache     dup conditions on glibc systems that allow overlapping allocations and function pointer overwrites.
    (CVE-2026-66032)

    libssh2 through 1.11.1, fixed in commit a13bb6c, contains a missing bounds check vulnerability that allows     a malicious SSH server to trigger an arbitrary-length heap out-of-bounds read and a free of an     uninitialized pointer via the publickey subsystem. In libssh2_publickey_list_fetch(), the version 1     response parser reads a server-controlled comment_len value and advances the parse pointer without     verifying sufficient bytes remain in the buffer, causing the out-of-bounds read to leak heap pointers from     adjacent allocations defeating ASLR, followed by heap allocator state corruption when the error cleanup     path frees an uninitialized pointer from a non-zeroed realloc() region. (CVE-2026-66034)

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.

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-2064 advisory.

    libgit2 Submodule path traversal (CVE-2026-53584)

    Unbounded Memory Allocation via Delta Object Result-Size Header (CVE-2026-53585)

    libgit2 version 1.9.4 and below is vulnerable to a heap out-of-bounds read in set_data() in     src/libgit2/transports/smart_pkt.c.

    The vulnerable code uses a fixed-size strncmp (smart_pkt.c:239) against the unvalidated capability buffer     of a smart-protocol pkt-line. When the bytes following the pkt-line in the contiguous receive buffer     happen to continue with ct-format=, the comparison spuriously matches, advancing format_str past the     pkt-line boundary. The following memchr(format_str, ' ', len - (format_str - line)) (smart_pkt.c:246) then     underflows its size_t size argument to ~SIZE_MAX and walks the heap looking for a space byte. An     unauthenticated remote attacker who controls (or man-in-the-middles) a Git server reached over     HTTP/HTTPS/SSH/git:// can trigger this on the FIRST ref-pkt of the refs advertisement, before any     capability negotiation has taken place. The OOB walk causes a process crash (SIGSEGV) when memchr enters     an unmapped page, and -- on heap layouts where memchr finds a stray space byte before crashing -- can     additionally drive the git_error_set(...'%.*s', format_len, format_str) formatter to copy a large window     of heap memory into the error string. (CVE-2026-53587)

    libssh2 through 1.11.1, fixed in commit 5e47761, contains a double-free vulnerability in the sftp_open()     function in src/sftp.c that allows a malicious SSH server to corrupt the heap of any authenticated client     opening an SFTP session. When a server responds to SSH_FXP_OPEN with SSH_FXP_STATUS containing FX_OK, the     response data buffer is freed, and if a subsequent sftp_packet_require() call returns a specific error     such as LIBSSH2_ERROR_CHANNEL_PACKET_EXCEEDED, the same pointer is freed a second time, enabling tcache     dup conditions on glibc systems that allow overlapping allocations and function pointer overwrites.
    (CVE-2026-66032)

    libssh2 through 1.11.1, fixed in commit a2ed82d, contains a pre-authentication integer underflow     vulnerability in the ssh2_cipher_crypt() function in src/openssl.c that allows a malicious SSH server to     crash any connecting client by negotiating AES-GCM ciphers during handshake. Attackers can exploit the     underflow in the expression computing blocksize minus aadlen minus authentication tag length to trigger an     out-of-bounds read and a memcpy call with a near-SIZE_MAX length argument, causing immediate process crash     before any authentication occurs. (CVE-2026-66033)

    libssh2 through 1.11.1, fixed in commit a13bb6c, contains a missing bounds check vulnerability that allows     a malicious SSH server to trigger an arbitrary-length heap out-of-bounds read and a free of an     uninitialized pointer via the publickey subsystem. In libssh2_publickey_list_fetch(), the version 1     response parser reads a server-controlled comment_len value and advances the parse pointer without     verifying sufficient bytes remain in the buffer, causing the out-of-bounds read to leak heap pointers from     adjacent allocations defeating ASLR, followed by heap allocator state corruption when the error cleanup     path frees an uninitialized pointer from a non-zeroed realloc() region. (CVE-2026-66034)

    libssh2 through 1.11.1, fixed in commit 42e33d8, contains a pre-authentication heap buffer overflow     vulnerability that allows a malicious SSH server to corrupt heap metadata in any connecting client by     sending a packet with a packet_length smaller than the cipher's block size during Encrypt-then-MAC cipher     negotiation. In the fullpacket() function in src/transport.c, the ETM path allocates a buffer of     packet_length bytes but copies blocksize minus one bytes via memcpy, causing an overflow that on 32-bit     glibc writes attacker-controlled bytes into an adjacent chunk's SIZE field, enabling tcache bin confusion,     overlapping live objects, and function pointer overwrite during the session handshake before     authentication. (CVE-2026-66035)

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.

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 version of Tencent Linux installed on the remote TencentOS Server 4 host is prior to tested version. It is, therefore, affected by multiple vulnerabilities as referenced in the TSSA-2026:0785 advisory.

    Package updates are available for TencentOS Server 4 that fix the following vulnerabilities:

    CVE-2026-66035:
    libssh2 through 1.11.1, fixed in commit 42e33d8, contains a pre-authentication heap buffer overflow     vulnerability that allows a malicious SSH server to corrupt heap metadata in any connecting client by     sending a packet with a packet_length smaller than the cipher's block size during Encrypt-then-MAC cipher     negotiation. In the fullpacket() function in src/transport.c, the ETM path allocates a buffer of     packet_length bytes but copies blocksize minus one bytes via memcpy, causing an overflow that on 32-bit     glibc writes attacker-controlled bytes into an adjacent chunk's SIZE field, enabling tcache bin confusion,     overlapping live objects, and function pointer overwrite during the session handshake before     authentication.

    CVE-2026-66034:
    libssh2 through 1.11.1, fixed in commit a13bb6c, contains a missing bounds check vulnerability that allows     a malicious SSH server to trigger an arbitrary-length heap out-of-bounds read and a free of an     uninitialized pointer via the publickey subsystem. In libssh2_publickey_list_fetch(), the version 1     response parser reads a server-controlled comment_len value and advances the parse pointer without     verifying sufficient bytes remain in the buffer, causing the out-of-bounds read to leak heap pointers from     adjacent allocations defeating ASLR, followed by heap allocator state corruption when the error cleanup     path frees an uninitialized pointer from a non-zeroed realloc() region.

    CVE-2026-66033:
    libssh2 through 1.11.1, fixed in commit a2ed82d, contains a pre-authentication integer underflow     vulnerability in the ssh2_cipher_crypt() function in src/openssl.c that allows a malicious SSH server to     crash any connecting client by negotiating AES-GCM ciphers during handshake.

    CVE-2026-66032:
    libssh2 through 1.11.1 contains a double-free vulnerability in the sftp_open() function in src/sftp.c that     allows a malicious SSH server to corrupt the heap of any authenticated client opening an SFTP session.
    When a server responds to SSH_FXP_OPEN with SSH_FXP_STATUS containing FX_OK, the response data buffer is     freed, and if a subsequent sftp_packet_require() call returns a specific error such as     LIBSSH2_ERROR_CHANNEL_PACKET_EXCEEDED, the same pointer is freed a second time, enabling tcache dup     conditions on glibc systems.

Tenable has extracted the preceding description block directly from the Tencent 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 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 a13bb6c, contains a missing bounds check vulnerability that allows     a malicious SSH server to trigger an arbitrary-length heap out-of-bounds read and a free of an     uninitialized pointer via the publickey subsystem. In libssh2_publickey_list_fetch(), the version 1     response parser reads a server-controlled comment_len value and advances the parse pointer without     verifying sufficient bytes remain in the buffer, causing the out-of-bounds read to leak heap pointers from     adjacent allocations defeating ASLR, followed by heap allocator state corruption when the error cleanup     path frees an uninitialized pointer from a non-zeroed realloc() region. (CVE-2026-66034)

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

ID	Name	Product	Family	Type	Severity
343114	Debian dla-4773 : libssh2-1 - security update	Nessus	Debian Local Security Checks	Local	high
341725	RHEL 7 : libssh2 (RHSA-2026:61752)	Nessus	Red Hat Local Security Checks	Local	high
338180	Unity Linux 20.1050e / 20.1060e / 20.1070e Security Update: libssh2 (UTSA-2026-102688)	Nessus	Unity Linux Local Security Checks	Local	high
337231	Amazon Linux 2 : libssh2, --advisory ALAS2-2026-3861 (ALAS-2026-3861)	Nessus	Amazon Linux Local Security Checks	Local	high
337217	Amazon Linux 2023 : libssh2, libssh2-devel (ALAS2023-2026-2056)	Nessus	Amazon Linux Local Security Checks	Local	high
337216	Amazon Linux 2023 : cargo-c (ALAS2023-2026-2064)	Nessus	Amazon Linux Local Security Checks	Local	high
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
333143	TencentOS Server 4: libssh2 (TSSA-2026:0785)	Nessus	Tencent Local Security Checks	Local	high
329538	Linux Distros Unpatched Vulnerability : CVE-2026-66034	Nessus	Misc.	Local	high

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