Double Free Vulnerability in OpenSSH Affects FIPS Mode Client Operations
CVE-2026-55653

4.3MEDIUM

Key Information:

Vendor

Red Hat
Status
Red Hat Enterprise Linux 10
Red Hat Enterprise Linux 6
Red Hat Enterprise Linux 7
Red Hat Enterprise Linux 8
Vendor
CVE Published:
23 June 2026

What is CVE-2026-55653?

A significant flaw has been identified in OpenSSH that allows a malicious SSH server to exploit a double free vulnerability through the Diffie-Hellman Group Exchange (DH-GEX) client path. This vulnerability becomes evident during the Federal Information Processing Standards (FIPS) mode known-group validation as the client interacts with attacker-controlled DH-GEX group parameters. If successfully exploited, this flaw can cause the termination of the client-side process, leading to a Denial of Service (DoS), which disrupts users' ability to connect securely.

References

https://access.redhat.com/security/cve/CVE-2026-55653
vdb-entryx_refsource_REDHAT
https://bugzilla.redhat.com/show_bug.cgi?id=2462351
issue-trackingx_refsource_REDHAT

CVSS V3.1

Score:
4.3
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
Required
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.