CVE-2026-55653
MEDIUM 4.3A 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).
No known exploitation, public exploit, or elevated probability at this time. Track for changes.
Exploitation likelihood
0.2%chance of exploitation in 30 days · 15th percentile
Impact if exploited
4.3CVSS 3.1 · MEDIUM
- ConfidentialityNone
- IntegrityNone
- AvailabilityLow
What an attacker needs
- ✓Access: Reachable over the network — no local access needed
- ✓Privileges: No account or privileges required
- ⚠User interaction: A user must take an action (click / open a file)
- ✓Complexity: No special conditions — reliably repeatable
✓ lowers the bar for an attacker · ⚠ raises it
Proof of concept & exploit code
- reference https://bugzilla.redhat.com/show_bug.cgi?id=2462351
- github-search Search GitHub for public PoC repos
Test against your own equipment
curl -s https://vulnpedia.com/cve/CVE-2026-55653/poc.jsonMachine-readable PoC index for this CVE (for automation).Listed for defensive triage, patch verification, and authorized testing on systems you own. Machine-readable: /cve/CVE-2026-55653/poc.json
Affected
Vendors Red Hat Openbsd Redhat
Products Red Hat Hardened Images Red Hat Enterprise Linux 10 Red Hat Enterprise Linux 6 Red Hat Enterprise Linux 7 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 9 Red Hat Openshift Container Platform 4 Openssh Hardened Images Openshift Container Platform Enterprise Linux
Weakness (CWE)
- CWE-415: Double Free
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
Known Affected Software Configurations
| Vendor | Product | Version range |
|---|---|---|
| Openbsd | Openssh | * |
| Redhat | Hardened Images | * |
| 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 |
All CVSS metrics
- MEDIUM 4.3 v3.1 · CNA Primary
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L - MEDIUM 4.3 v3.1 · NVD Secondary
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L - MEDIUM 6.5 v3.1 · NVD Primary
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H