CVE-2026-55653 Details
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).
A double free vulnerability has been identified in OpenSSH, specifically in the Diffie-Hellman Group Exchange (DH-GEX) client path. This vulnerability arises when a malicious SSH server exploits the client's handling of DH-GEX group parameters during FIPS mode known-group validation. The flaw leads to a double free condition, causing the client process to terminate and resulting in a denial-of-service (DoS) situation.
OpenSSH clients in FIPS mode should avoid using the 'diffie-hellman-group-exchange-sha256' key exchange algorithm. This can be done by specifying a different set of allowed key exchange algorithms in the SSH configuration file. Additionally, refrain from using non-fatal client flows, such as 'ssh-keyscan', with untrusted SSH servers while FIPS mode is active.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Jun 23, 2026References to Advisories, Solutions, and Tools
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Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-415 | Double Free | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| openbsd openssh | All versions |
CPE
Remediation
| |
| redhat hardened images | All versions |
CPE
Remediation
| |
| redhat openshift container platform | 4.0 |
CPE
Remediation
| |
| redhat enterprise linux | 6.0 7.0 8.0 9.0 10.0 |
CPE
Remediation
| |
Change History
12 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Sep 1, 2026 | CVE Modified | [email protected] |
| Aug 31, 2026 | CVE Modified | [email protected] |
| Aug 25, 2026 | CVE Modified | [email protected] |
| Aug 24, 2026 | CVE Modified | [email protected] |
| Aug 21, 2026 | CVE Modified | [email protected] |
| Aug 12, 2026 | CVE Modified | [email protected] |
| Jul 30, 2026 | CVE Modified | [email protected] |
| Jul 30, 2026 | CVE Modified | [email protected] |
| Jul 8, 2026 | CVE Modified | [email protected] |
| Jun 25, 2026 | Initial Analysis | [email protected] |
| Jun 23, 2026 | CVE Modified | CISA-ADP |
| Jun 23, 2026 | New CVE Received | [email protected] |