CVE-2026-55653

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).

CVSS breakdown

Affected products

• openbsd / openssh
• redhat / enterprise_linux10.0 – 10.0
• redhat / enterprise_linux8.0 – 8.0
• redhat / enterprise_linux9.0 – 9.0
• redhat / enterprise_linux6.0 – 6.0
• redhat / enterprise_linux7.0 – 7.0
• redhat / hardened_images
• redhat / openshift_container_platform4.0 – 4.0

References

• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:36759
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:47755
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:47756
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:47757
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:54387
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:58981
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:76748
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:76993
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:80513
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82749
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82750
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82751
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82752
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82753
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82754
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82755
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82756
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82757
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82758
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82759
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82761
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82762
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82763
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82897
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82898
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82899
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82900
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82901
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82902
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82903
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82904
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82907
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82908
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82909
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82910
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82912
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82913
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82914
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82915
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82916
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82917
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82918
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82920
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82921
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82922
• VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:82923
• VENDOR_ADVISORYhttps://access.redhat.com/security/cve/CVE-2026-55653
• MISChttps://bugzilla.redhat.com/show_bug.cgi?id=2462351