A flaw was found in OpenSSH. A malicious SSH server can exploit a double free vulnerability in the Diffie-Hellman Group Exchange (DH-GEX) client path. This occurs during FIPS (Federal Information Processing Standards) mode known-group validation when the client processes attacker-controlled DH-GEX group parameters. Successful exploitation leads to client-side process termination, resulting in a Denial of Service (DoS).

The remote Oracle Linux 9 host has packages installed that are affected by multiple vulnerabilities as referenced in the ELSA-2026-47756 advisory.

    - CVE-2026-59996: Fix remote glob result of '..' causing files to be placed       in unintended parent directories when scp performs remote-to-remote copy       via the local host       Resolves: RHEL-193178
    - CVE-2026-60002: Fix use-after-free in cached hostkey during key re-exchange       Resolves: RHEL-193024
    - CVE-2026-55653: Fix double free in openssh DH-GEX client path during       FIPS known-group validation that leads to client-side denial of service       Resolves: RHEL-186439
    - CVE-2026-55654: Fix heap out-of-bounds read during GSSAPI indicator       cleanup due to missing NULL terminator       Resolves: RHEL-185836

Tenable has extracted the preceding description block directly from the Oracle 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 MiracleLinux 9 host has packages installed that are affected by multiple vulnerabilities as referenced in the AXSA:2026-1533:08 advisory.

    * openssh: Local MITM of X11 forwarding via abstract UNIX socket pre-binding in MIRACLE LINUX OpenSSH     client versions (CVE-2026-55655)
      * openssh: Double free in MIRACLE LINUX versions of OpenSSH DH-GEX client path during FIPS known-group     validation leads to client-side denial of service (CVE-2026-55653)
      * openssh: Heap out-of-bounds read in MIRACLE LINUX versions of OpenSSH GSSAPI indicator cleanup due to     missing NULL sentinel termination (CVE-2026-55654)
      * openssh: OpenSSH: Use-after-free vulnerability during host key re-exchange on the client side     (CVE-2026-60002)
      * openssh: OpenSSH: `scp` file misplacement vulnerability during remote copy (CVE-2026-59996)

Tenable has extracted the preceding description block directly from the MiracleLinux 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 3 host is prior to tested version. It is, therefore, affected by multiple vulnerabilities as referenced in the TSSA-2026:0848 advisory.

    Package updates are available for TencentOS Server 3 that fix the following vulnerabilities:

    CVE-2026-55653:
    A flaw was found in OpenSSH. A malicious SSH server can exploit a double free vulnerability in the Diffie-     Hellman Group Exchange (DH-GEX) client path. This occurs during FIPS (Federal Information Processing     Standards) mode known-group validation when the client processes attacker-controlled DH-GEX group     parameters. Successful exploitation leads to client-side process termination, resulting in a Denial of     Service (DoS).

    CVE-2026-55655:
    A flaw was found in OpenSSH. A local unprivileged attacker on a Linux client host can hijack client-side     X11 forwarding connections. This is possible by pre-binding the preferred abstract X socket name when X11     forwarding is enabled and a local UNIX-domain X socket is used. A successful attack can compromise the     confidentiality of forwarded X11 traffic, including sensitive window contents and input, and may allow     some manipulation of the forwarded session.

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 remote Alibaba Cloud Linux 3 host has packages installed that are affected by multiple vulnerabilities as referenced in the ALINUX3-SA-2026:0246 advisory.

    Package updates are available for Alibaba Cloud Linux 3 that fix the following vulnerabilities:

    CVE-2026-55653:
    A flaw was found in OpenSSH. A malicious SSH server can exploit a double free vulnerability in the Diffie-     Hellman Group Exchange (DH-GEX) client path. This occurs during FIPS (Federal Information Processing     Standards) mode known-group validation when the client processes attacker-controlled DH-GEX group     parameters. Successful exploitation leads to client-side process termination, resulting in a Denial of     Service (DoS).

    CVE-2026-55655:
    A flaw was found in OpenSSH. A local unprivileged attacker on a Linux client host can hijack client-side     X11 forwarding connections. This is possible by pre-binding the preferred abstract X socket name when X11     forwarding is enabled and a local UNIX-domain X socket is used. A successful attack can compromise the     confidentiality of forwarded X11 traffic, including sensitive window contents and input, and may allow     some manipulation of the forwarded session.

Tenable has extracted the preceding description block directly from the Alibaba Cloud 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.

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-2031 advisory.

    A flaw was found in OpenSSH. A malicious SSH server can exploit a double free vulnerability in the Diffie-     Hellman Group Exchange (DH-GEX) client path. This occurs during FIPS (Federal Information Processing     Standards) mode known-group validation when the client processes attacker-controlled DH-GEX group     parameters. Successful exploitation leads to client-side process termination, resulting in a Denial of     Service (DoS). (CVE-2026-55653)

    A flaw was found in OpenSSH. A local unprivileged attacker on a Linux client host can hijack client-side     X11 forwarding connections. This is possible by pre-binding the preferred abstract X socket name when X11     forwarding is enabled and a local UNIX-domain X socket is used. A successful attack can compromise the     confidentiality of forwarded X11 traffic, including sensitive window contents and input, and may allow     some manipulation of the forwarded session. (CVE-2026-55655)

    scp in OpenSSH before 10.4 may place a file in the parent directory of an intended directory when the copy     occurs between two remote destinations. (CVE-2026-59996)

    ssh in OpenSSH before 10.4 can have a use-after-free when a server changes its host key during a key re-     exchange. (This outcome occurs only on the client side.) (CVE-2026-60002)

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 MiracleLinux 8 host has packages installed that are affected by multiple vulnerabilities as referenced in the AXSA:2026-1438:07 advisory.

    * openssh: Local MITM of X11 forwarding via abstract UNIX socket pre-binding in Asianux Server OpenSSH     client versions (CVE-2026-55655)
      * openssh: Double free in Asianux Server versions of OpenSSH DH-GEX client path during FIPS known-group     validation leads to client-side denial of service (CVE-2026-55653)

Tenable has extracted the preceding description block directly from the MiracleLinux 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 Oracle Linux 8 host has packages installed that are affected by multiple vulnerabilities as referenced in the ELSA-2026-47755 advisory.

    - CVE-2026-55653: Fix double free in openssh DH-GEX client path during       FIPS known-group validation that leads to client-side denial of service       Resolves: RHEL-185775

Tenable has extracted the preceding description block directly from the Oracle 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 AlmaLinux 9 host has packages installed that are affected by multiple vulnerabilities as referenced in the ALSA-2026:47756 advisory.

    * openssh: Local MITM of X11 forwarding via abstract UNIX socket pre-binding in AlmaLinux OpenSSH client     versions (CVE-2026-55655)
      * openssh: Double free in AlmaLinux versions of OpenSSH DH-GEX client path during FIPS known-group     validation leads to client-side denial of service (CVE-2026-55653)
      * openssh: Heap out-of-bounds read in AlmaLinux versions of OpenSSH GSSAPI indicator cleanup due to     missing NULL sentinel termination (CVE-2026-55654)
      * openssh: OpenSSH: Use-after-free vulnerability during host key re-exchange on the client side     (CVE-2026-60002)
      * openssh: OpenSSH: `scp` file misplacement vulnerability during remote copy (CVE-2026-59996)

Tenable has extracted the preceding description block directly from the AlmaLinux 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 RockyLinux 9 host has packages installed that are affected by multiple vulnerabilities as referenced in the RLSA-2026:47756 advisory.

    * openssh: Local MITM of X11 forwarding via abstract UNIX socket pre-binding in Rocky Linux OpenSSH client     versions (CVE-2026-55655)

    * openssh: Double free in Rocky Linux versions of OpenSSH DH-GEX client path during FIPS known-group     validation leads to client-side denial of service (CVE-2026-55653)

    * openssh: Heap out-of-bounds read in Rocky Linux versions of OpenSSH GSSAPI indicator cleanup due to     missing NULL sentinel termination (CVE-2026-55654)

    * openssh: OpenSSH: Use-after-free vulnerability during host key re-exchange on the client side     (CVE-2026-60002)

    * openssh: OpenSSH: `scp` file misplacement vulnerability during remote copy (CVE-2026-59996)

Tenable has extracted the preceding description block directly from the RockyLinux 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 AlmaLinux 10 host has packages installed that are affected by multiple vulnerabilities as referenced in the ALSA-2026:47757 advisory.

    * openssh: Local MITM of X11 forwarding via abstract UNIX socket pre-binding in AlmaLinux OpenSSH client     versions (CVE-2026-55655)
      * openssh: Double free in AlmaLinux versions of OpenSSH DH-GEX client path during FIPS known-group     validation leads to client-side denial of service (CVE-2026-55653)
      * openssh: Heap out-of-bounds read in AlmaLinux versions of OpenSSH GSSAPI indicator cleanup due to     missing NULL sentinel termination (CVE-2026-55654)
      * openssh: OpenSSH: Use-after-free vulnerability during host key re-exchange on the client side     (CVE-2026-60002)
      * openssh: OpenSSH: `scp` file misplacement vulnerability during remote copy (CVE-2026-59996)

Tenable has extracted the preceding description block directly from the AlmaLinux 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 Oracle Linux 10 host has packages installed that are affected by multiple vulnerabilities as referenced in the ELSA-2026-47757 advisory.

    - CVE-2026-59996: Fix remote glob result of '..' causing files to be placed       in unintended parent directories when scp performs remote-to-remote copy       via the local host       Resolves: RHEL-193170
    - CVE-2026-60002: Fix use-after-free in cached hostkey during key re-exchange       Resolves: RHEL-193016
    - CVE-2026-55653: Fix double free in openssh DH-GEX client path during       FIPS known-group validation that leads to client-side denial of service       Resolves: RHEL-186435
    - CVE-2026-55654: Fix heap out-of-bounds read during GSSAPI indicator       cleanup due to missing NULL terminator       Resolves: RHEL-185826

Tenable has extracted the preceding description block directly from the Oracle 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 Redhat Enterprise Linux 8 host has packages installed that are affected by multiple vulnerabilities as referenced in the RHSA-2026:47755 advisory.

    OpenSSH is an SSH protocol implementation supported by a number of Linux, UNIX, and similar operating     systems. It includes the core files necessary for both the OpenSSH client and server.

    Security Fix(es):

    * openssh: Local MITM of X11 forwarding via abstract UNIX socket pre-binding in Red Hat Enterprise Linux     OpenSSH client versions (CVE-2026-55655)

    * openssh: Double free in Red Hat Enterprise Linux versions of OpenSSH DH-GEX client path during FIPS     known-group validation leads to client-side denial of service (CVE-2026-55653)

    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 remote Redhat Enterprise Linux 9 host has packages installed that are affected by multiple vulnerabilities as referenced in the RHSA-2026:47756 advisory.

    OpenSSH is an SSH protocol implementation supported by a number of Linux, UNIX, and similar operating     systems. It includes the core files necessary for both the OpenSSH client and server.

    Security Fix(es):

    * openssh: Local MITM of X11 forwarding via abstract UNIX socket pre-binding in Red Hat Enterprise Linux     OpenSSH client versions (CVE-2026-55655)

    * openssh: Double free in Red Hat Enterprise Linux versions of OpenSSH DH-GEX client path during FIPS     known-group validation leads to client-side denial of service (CVE-2026-55653)

    * openssh: Heap out-of-bounds read in Red Hat Enterprise Linux versions of OpenSSH GSSAPI indicator     cleanup due to missing NULL sentinel termination (CVE-2026-55654)

    * openssh: OpenSSH: Use-after-free vulnerability during host key re-exchange on the client side     (CVE-2026-60002)

    * openssh: OpenSSH: `scp` file misplacement vulnerability during remote copy (CVE-2026-59996)

    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 remote Redhat Enterprise Linux 10 host has packages installed that are affected by multiple vulnerabilities as referenced in the RHSA-2026:47757 advisory.

    OpenSSH is an SSH protocol implementation supported by a number of Linux, UNIX, and similar operating     systems. It includes the core files necessary for both the OpenSSH client and server.

    Security Fix(es):

    * openssh: Local MITM of X11 forwarding via abstract UNIX socket pre-binding in Red Hat Enterprise Linux     OpenSSH client versions (CVE-2026-55655)

    * openssh: Double free in Red Hat Enterprise Linux versions of OpenSSH DH-GEX client path during FIPS     known-group validation leads to client-side denial of service (CVE-2026-55653)

    * openssh: Heap out-of-bounds read in Red Hat Enterprise Linux versions of OpenSSH GSSAPI indicator     cleanup due to missing NULL sentinel termination (CVE-2026-55654)

    * openssh: OpenSSH: Use-after-free vulnerability during host key re-exchange on the client side     (CVE-2026-60002)

    * openssh: OpenSSH: `scp` file misplacement vulnerability during remote copy (CVE-2026-59996)

    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 remote RockyLinux 8 host has packages installed that are affected by multiple vulnerabilities as referenced in the RLSA-2026:47755 advisory.

    * openssh: Local MITM of X11 forwarding via abstract UNIX socket pre-binding in Rocky Linux OpenSSH client     versions (CVE-2026-55655)

    * openssh: Double free in Rocky Linux versions of OpenSSH DH-GEX client path during FIPS known-group     validation leads to client-side denial of service (CVE-2026-55653)

Tenable has extracted the preceding description block directly from the RockyLinux 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 RockyLinux 10 host has packages installed that are affected by multiple vulnerabilities as referenced in the RLSA-2026:47757 advisory.

    * openssh: Local MITM of X11 forwarding via abstract UNIX socket pre-binding in Rocky Linux OpenSSH client     versions (CVE-2026-55655)

    * openssh: Double free in Rocky Linux versions of OpenSSH DH-GEX client path during FIPS known-group     validation leads to client-side denial of service (CVE-2026-55653)

    * openssh: Heap out-of-bounds read in Rocky Linux versions of OpenSSH GSSAPI indicator cleanup due to     missing NULL sentinel termination (CVE-2026-55654)

    * openssh: OpenSSH: Use-after-free vulnerability during host key re-exchange on the client side     (CVE-2026-60002)

    * openssh: OpenSSH: `scp` file misplacement vulnerability during remote copy (CVE-2026-59996)

Tenable has extracted the preceding description block directly from the RockyLinux 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-2026-95b955a09b advisory.

    - CVE-2026-55653: Fix double free in openssh DH-GEX client path during FIPS known-group validation that     leads to client-side denial of service
    - CVE-2026-55654: Fix heap out-of-bounds read during GSSAPI indicator cleanup due to missing NULL     terminator
    - CVE-2026-55655: Fix MITM of X11 forwarding via abstract UNIX socket pre-binding

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-a80275b42d advisory.

    Improve GSS KEX algorithms documentation

    ----

    - CVE-2026-55653: Fix double free in openssh DH-GEX client path during FIPS known-group validation that     leads to client-side denial of service
    - CVE-2026-55654: Fix heap out-of-bounds read during GSSAPI indicator cleanup due to missing NULL     terminator
    - CVE-2026-55655: Fix MITM of X11 forwarding via abstract UNIX socket pre-binding

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 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 OpenSSH. A malicious SSH server can exploit a double free vulnerability in the Diffie-     Hellman Group Exchange (DH-GEX) client path. This occurs during FIPS (Federal Information Processing     Standards) mode known-group validation when the client processes attacker-controlled DH-GEX group     parameters. Successful exploitation leads to client-side process termination, resulting in a Denial of     Service (DoS). (CVE-2026-55653)

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

ID	Name	Product	Family	Type	Severity
335463	Oracle Linux 9 : openssh (ELSA-2026-47756)	Nessus	Oracle Linux Local Security Checks	Local	critical
335338	MiracleLinux 9 : openssh-9.9p1-9.el9_8.ML.1 (AXSA:2026-1533:08)	Nessus	Miracle Linux Local Security Checks	Local	critical
335135	TencentOS Server 3: openssh (TSSA-2026:0848)	Nessus	Tencent Local Security Checks	Local	medium
333568	Alibaba Cloud Linux 3 : 0246: openssh (ALINUX3-SA-2026:0246)	Nessus	Alibaba Cloud Linux Local Security Checks	Local	medium
332008	Amazon Linux 2023 : openssh, openssh-clients, openssh-keycat (ALAS2023-2026-2031)	Nessus	Amazon Linux Local Security Checks	Local	critical
331872	MiracleLinux 8 : openssh-8.0p1-30.el8_10 (AXSA:2026-1438:07)	Nessus	Miracle Linux Local Security Checks	Local	medium
331539	Oracle Linux 8 : openssh (ELSA-2026-47755)	Nessus	Oracle Linux Local Security Checks	Local	medium
331475	AlmaLinux 9 : openssh (ALSA-2026:47756)	Nessus	Alma Linux Local Security Checks	Local	critical
331313	RockyLinux 9 : openssh (RLSA-2026:47756)	Nessus	Rocky Linux Local Security Checks	Local	critical
331288	AlmaLinux 10 : openssh (ALSA-2026:47757)	Nessus	Alma Linux Local Security Checks	Local	critical
331287	Oracle Linux 10 : openssh (ELSA-2026-47757)	Nessus	Oracle Linux Local Security Checks	Local	critical
330865	RHEL 8 : openssh (RHSA-2026:47755)	Nessus	Red Hat Local Security Checks	Local	medium
330864	RHEL 9 : openssh (RHSA-2026:47756)	Nessus	Red Hat Local Security Checks	Local	critical
330850	RHEL 10 : openssh (RHSA-2026:47757)	Nessus	Red Hat Local Security Checks	Local	critical
330845	RockyLinux 8 : openssh (RLSA-2026:47755)	Nessus	Rocky Linux Local Security Checks	Local	medium
330844	RockyLinux 10 : openssh (RLSA-2026:47757)	Nessus	Rocky Linux Local Security Checks	Local	critical
326360	Fedora 43 : openssh (2026-95b955a09b)	Nessus	Fedora Local Security Checks	Local	medium
325835	Fedora 44 : openssh (2026-a80275b42d)	Nessus	Fedora Local Security Checks	Local	medium
322159	Linux Distros Unpatched Vulnerability : CVE-2026-55653	Nessus	Misc.	Local	medium

Detections

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CVE-2026-55653

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Tenable Plugins

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