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).

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Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.


Workaround

To mitigate this issue, OpenSSH clients operating in FIPS mode should avoid negotiating the `diffie-hellman-group-exchange-sha256` key exchange algorithm. This can be achieved by explicitly listing allowed key exchange algorithms in the client's SSH configuration file (e.g., `/etc/ssh/ssh_config` or `~/.ssh/config`), ensuring `diffie-hellman-group-exchange-sha256` is *not* included. For example, to use a subset of common algorithms, you might configure: ``` KexAlgorithms curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group14-sha1 ``` (Note: The above example `KexAlgorithms` list is illustrative and should be adjusted based on your environment's security requirements.) Additionally, avoid using non-fatal client flows, such as `ssh-keyscan`, against untrusted SSH servers while FIPS mode is enabled. Changes to `ssh_config` will take effect for new SSH connections.

References
Link Providers
https://access.redhat.com/errata/RHSA-2026:36759 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:47755 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:47756 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:47757 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:54387 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:58981 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:76748 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:76993 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:80513 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82749 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82750 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82751 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82752 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82753 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82754 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82755 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82756 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82757 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82758 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82759 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82761 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82762 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82763 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82897 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82898 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82899 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82900 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82901 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82902 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82903 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82904 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82907 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82908 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82909 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82910 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82912 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82913 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82914 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82915 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82916 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82917 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82918 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82920 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82921 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82922 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:82923 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:89739 cve-icon cve-icon
https://access.redhat.com/errata/RHSA-2026:91232 cve-icon cve-icon
https://access.redhat.com/security/cve/CVE-2026-55653 cve-icon cve-icon
https://bugzilla.redhat.com/show_bug.cgi?id=2462351 cve-icon cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2026-55653 cve-icon
https://www.cve.org/CVERecord?id=CVE-2026-55653 cve-icon
History

Fri, 30 Oct 2026 08:00:00 +0000

Type Values Removed Values Added
CPEs cpe:/a:redhat:openshift:5

Thu, 29 Oct 2026 22:30:00 +0000

Type Values Removed Values Added
References

Mon, 26 Oct 2026 03:45:00 +0000

Type Values Removed Values Added
CPEs cpe:/a:redhat:rhel_e4s:9.2::appstream
cpe:/o:redhat:rhel_e4s:9.2::baseos
References

Wed, 14 Oct 2026 19:30:00 +0000

Type Values Removed Values Added
CPEs cpe:/a:redhat:openshift_ai:3.0::el9
cpe:/a:redhat:openshift_ai:3.2::el9
cpe:/a:redhat:openshift_ai:3.3::el9
cpe:/a:redhat:openshift_ai:3.5::el9
References

Wed, 14 Oct 2026 07:00:00 +0000

Type Values Removed Values Added
First Time appeared Redhat openshift Ai
CPEs cpe:/a:redhat:openshift_ai:3.4::el9
Vendors & Products Redhat openshift Ai
References

Mon, 12 Oct 2026 08:15:00 +0000

Type Values Removed Values Added
First Time appeared Redhat rhel Eus
CPEs cpe:/a:redhat:rhel_eus:9.6::appstream
cpe:/o:redhat:rhel_eus:9.6::baseos
Vendors & Products Redhat rhel Eus
References

Wed, 07 Oct 2026 02:45:00 +0000

Type Values Removed Values Added
First Time appeared Redhat rhel E4s
CPEs cpe:/a:redhat:rhel_e4s:9.4::appstream
cpe:/o:redhat:rhel_e4s:9.4::baseos
Vendors & Products Redhat rhel E4s
References

Tue, 06 Oct 2026 15:30:00 +0000

Type Values Removed Values Added
First Time appeared Redhat enterprise Linux Eus
CPEs cpe:/o:redhat:enterprise_linux_eus:10.0
Vendors & Products Redhat enterprise Linux Eus
References

Tue, 25 Aug 2026 10:00:00 +0000

Type Values Removed Values Added
References

Wed, 12 Aug 2026 16:00:00 +0000

Type Values Removed Values Added
First Time appeared Redhat rhui
CPEs cpe:/a:redhat:rhui:5::el9
Vendors & Products Redhat rhui
References

Thu, 30 Jul 2026 09:00:00 +0000

Type Values Removed Values Added
CPEs cpe:/o:redhat:enterprise_linux:10
cpe:/o:redhat:enterprise_linux:9
cpe:/a:redhat:enterprise_linux:9::appstream
cpe:/o:redhat:enterprise_linux:10.2
cpe:/o:redhat:enterprise_linux:9::baseos
References

Thu, 30 Jul 2026 06:15:00 +0000

Type Values Removed Values Added
CPEs cpe:/o:redhat:enterprise_linux:8 cpe:/a:redhat:enterprise_linux:8::appstream
cpe:/o:redhat:enterprise_linux:8::baseos
References

Wed, 08 Jul 2026 14:15:00 +0000

Type Values Removed Values Added
References

Wed, 24 Jun 2026 16:45:00 +0000

Type Values Removed Values Added
First Time appeared Openssh
Openssh openssh
Redhat hardened Images
Redhat openshift Container Platform
Vendors & Products Openssh
Openssh openssh
Redhat hardened Images
Redhat openshift Container Platform

Tue, 23 Jun 2026 15:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Tue, 23 Jun 2026 12:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

threat_severity

Moderate


Tue, 23 Jun 2026 03:45:00 +0000

Type Values Removed Values Added
Description 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).
Title 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
First Time appeared Redhat
Redhat enterprise Linux
Redhat hummingbird
Redhat openshift
Weaknesses CWE-415
CPEs cpe:/a:redhat:hummingbird:1
cpe:/a:redhat:openshift:4
cpe:/o:redhat:enterprise_linux:10
cpe:/o:redhat:enterprise_linux:6
cpe:/o:redhat:enterprise_linux:7
cpe:/o:redhat:enterprise_linux:8
cpe:/o:redhat:enterprise_linux:9
Vendors & Products Redhat
Redhat enterprise Linux
Redhat hummingbird
Redhat openshift
References
Metrics cvssV3_1

{'score': 4.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: redhat

Published:

Updated: 2026-10-30T07:43:00.763Z

Reserved: 2026-06-16T23:55:05.737Z

Link: CVE-2026-55653

cve-icon Vulnrichment

Updated: 2026-06-23T14:30:56.850Z

cve-icon NVD

Status : Modified

Published: 2026-06-23T04:17:36.600

Modified: 2026-10-30T08:16:57.497

Link: CVE-2026-55653

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-06-22T23:17:43Z

Links: CVE-2026-55653 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-06-24T16:06:37Z

Weaknesses