Vulnerability record/PUBLISHED/Published Jun 23, 2026 03:36:22 UTC

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).

Base score4.3/ 10

SeverityMediumCVSS 3.1

Exploitability / impact

CVSS metric breakdown

Vector-derived attributes

Base severityMedium

Attack vectorNetworkAV

Attack complexityLowAC

Privileges requiredNonePR

User interactionRequiredUI

ScopeUnchangedS

Confidentiality impactNoneC

Integrity impactNoneI

Availability impactLowA

CVSS vector stringCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L

CVSS communicates standardized severity and impact characteristics. It does not establish whether a system is exploitable in your specific environment.

Record context

CVE Numbering Authorityredhat

Last updatedOct 26, 2026 03:26:59 UTC

PublishedJun 23, 2026 03:36:22 UTC

ReservedJun 16, 2026 23:55:05 UTC

Credits

This issue was discovered by In partnership with Red Hat (Aisle.com).