CVE-2026-55653

Name: CVE-2026-55653
Creator: NVD / NIST
Published: 2026-06-23T04:17:36.6+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.5/10EPSS 0.20%

Last modified Jun 25, 2026

CVE-2026-55653 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. 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. EPSS estimates a 0.20% chance of exploitation in the next 30 days.

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).

Metrics

CVSS 3.1

6.5/10

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

EPSS Probability

0.20%

10.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-415

Affected Software

Vendor	Product	Versions
Openbsd	Openssh	All versions
Redhat	Hardened Images	All versions
Redhat	Openshift Container Platform	4.0
Redhat	Enterprise Linux	6.0
Redhat	Enterprise Linux	7.0
Redhat	Enterprise Linux	8.0
Redhat	Enterprise Linux	9.0
Redhat	Enterprise Linux	10.0

References

https://access.redhat.com/security/cve/CVE-2026-55653Vendor Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=2462351Exploit, Issue Tracking, Vendor Advisory

Timeline

Published: Jun 23, 2026
Last Modified: Jun 25, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-55653?

How severe is CVE-2026-55653?

CVE-2026-55653 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 0.20% probability of exploitation in the next 30 days.

How do I fix CVE-2026-55653?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-55653?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST