A flaw was found in libssh. Logic errors in automatic certificate-based public key authentication can cause libssh clients to loop indefinitely when configured certificates are missing or repeatedly rejected by a server, leading to denial of service.

The remote Debian 13 host has packages installed that are affected by multiple vulnerabilities as referenced in the dsa-6410 advisory.

    - -------------------------------------------------------------------------     Debian Security Advisory DSA-6410-1                   security@debian.org     https://www.debian.org/security/                     Salvatore Bonaccorso     August 02, 2026                       https://www.debian.org/security/faq
    - -------------------------------------------------------------------------

    Package        : libssh     CVE ID         : CVE-2026-0964 CVE-2026-0965 CVE-2026-0966 CVE-2026-0967                      CVE-2026-0968 CVE-2026-3731 CVE-2026-15370 CVE-2026-59843                      CVE-2026-59844 CVE-2026-59845 CVE-2026-59846 CVE-2026-59847                      CVE-2026-59848 CVE-2026-59849 CVE-2026-59850     Debian Bug     : 1127693 1142537

    Several vulnerabilities were discovered in libssh, a tiny C SSH library,     which may result in denial of service, information disclosure and     potentially the execution of arbitrary code.

    For the stable distribution (trixie), these problems have been fixed in     version 0.11.5-0+deb13u1.

    We recommend that you upgrade your libssh packages.

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

    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 remote SUSE Linux SLES16 / SLES_SAP16 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:22956-1 advisory.

    - CVE-2026-15370: stack buffer overflow in SFTP server longname construction (bsc#1272162).
    - CVE-2026-59843: denial of service via zero advertised channel packet size (bsc#1272164).
    - CVE-2026-59844: denial of service via oversized SFTP read length (bsc#1272165).
    - CVE-2026-59845: denial of service via unchecked ProxyCommand fork() failure (bsc#1272166).
    - CVE-2026-59846: information disclosure via ProxyCommand %r username expansion (bsc#1272167).
    - CVE-2026-59847: integrity downgrade via OpenSSL AES-GCM tag verification (bsc#1272168).
    - CVE-2026-59848: denial of service via SFTP responses with unknown request IDs (bsc#1272169).
    - CVE-2026-59849: denial of service via automatic certificate authentication loop (bsc#1272170).
    - CVE-2026-59850: use-after-free via data callbacks on closed channels (bsc#1272171).

    Changes for libssh:

    - Update to 0.11.5:

     * Zero-initialize every ssh_string
     * Fix compatibility with C23 / gcc16
     * Fix multiple memory leaks, null checks, and error checks
     * Validate peer public key in DH key exchange
     * Avoid remote window overflow
     * Avoid off-by-one overflow during kbdint authentication
     * Avoid logging uninitialized sequence numbers
     * Avoid double conversion of SFTP version number
     * Send correct SFTP server version number
     * Avoid handling repeated SFTP INIT messages
     * Harmonize return values from SFTP server callbacks

    - Update %suse_version checks for SLES 16.x (jsc#PED-15815)

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 openSUSE 16 host has packages installed that are affected by multiple vulnerabilities as referenced in the openSUSE-SU-2026:21444-1 advisory.

    - CVE-2026-15370: stack buffer overflow in SFTP server longname construction (bsc#1272162).
    - CVE-2026-59843: denial of service via zero advertised channel packet size (bsc#1272164).
    - CVE-2026-59844: denial of service via oversized SFTP read length (bsc#1272165).
    - CVE-2026-59845: denial of service via unchecked ProxyCommand fork() failure (bsc#1272166).
    - CVE-2026-59846: information disclosure via ProxyCommand %r username expansion (bsc#1272167).
    - CVE-2026-59847: integrity downgrade via OpenSSL AES-GCM tag verification (bsc#1272168).
    - CVE-2026-59848: denial of service via SFTP responses with unknown request IDs (bsc#1272169).
    - CVE-2026-59849: denial of service via automatic certificate authentication loop (bsc#1272170).
    - CVE-2026-59850: use-after-free via data callbacks on closed channels (bsc#1272171).

    Changes for libssh:

    - Update to 0.11.5:

     * Zero-initialize every ssh_string
     * Fix compatibility with C23 / gcc16
     * Fix multiple memory leaks, null checks, and error checks
     * Validate peer public key in DH key exchange
     * Avoid remote window overflow
     * Avoid off-by-one overflow during kbdint authentication
     * Avoid logging uninitialized sequence numbers
     * Avoid double conversion of SFTP version number
     * Send correct SFTP server version number
     * Avoid handling repeated SFTP INIT messages
     * Harmonize return values from SFTP server callbacks

    - Update %suse_version checks for SLES 16.x (jsc#PED-15815)

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 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 libssh. Logic errors in automatic certificate-based public key authentication can     cause libssh clients to loop indefinitely when configured certificates are missing or repeatedly rejected     by a server, leading to denial of service. (CVE-2026-59849)

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

The remote Fedora 43 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2026-063caa9112 advisory.

    New upstream security release (#2503148)


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 Fedora 44 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2026-0e46c91ccf advisory.

    New upstream security release


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 host is prior to 0.11.5 / 0.12.1. It is, therefore, affected by multiple vulnerabilities as referenced in the SSA:2026-202-01 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
331648	Debian dsa-6410 : libssh-4 - security update	Nessus	Debian Local Security Checks	Local	medium
330564	SUSE SLES16 Security Update : libssh (SUSE-SU-2026:22956-1)	Nessus	SuSE Local Security Checks	Local	high
330077	openSUSE 16 Security Update : libssh (openSUSE-SU-2026:21444-1)	Nessus	SuSE Local Security Checks	Local	high
329584	Linux Distros Unpatched Vulnerability : CVE-2026-59849	Nessus	Misc.	Local	high
329166	Fedora 43 : libssh (2026-063caa9112)	Nessus	Fedora Local Security Checks	Local	high
329159	Fedora 44 : libssh (2026-0e46c91ccf)	Nessus	Fedora Local Security Checks	Local	high
328881	Slackware Linux 15.0 / current libssh Multiple Vulnerabilities (SSA:2026-202-01)	Nessus	Slackware Local Security Checks	Local	high

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