Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:LSummary
CVE-2026-55653 is a medium-severity Double Free (CWE-415) vulnerability in Redhat Enterprise Linux. Its CVSS base score is 4.3 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 16th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to SI-2 (Flaw Remediation) and CM-7 (Least Functionality) — see the control section below for these in your framework.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-38412
Vulnerability Data
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…
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DH-GEX group parameters. Successful exploitation leads to client-side process termination, resulting in a Denial of Service (DoS).
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Double-free in OpenSSH client DH-GEX path directly enables application exploitation resulting in process termination/DoS.
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
Mitigating Controls (NIST 800-53 r5) AI
Directly requires patching the double-free flaw in the OpenSSH DH-GEX client code before an untrusted server can trigger it.
Disables or restricts use of DH-GEX (or non-approved groups) in the SSH client configuration so the vulnerable code path is never exercised.
Mandates approved cryptographic algorithms and key-exchange methods, preventing the client from accepting attacker-supplied DH parameters during FIPS validation.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly prevent double-free errors via static analysis, safe memory APIs, and testing.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development can detect double-free conditions before release.
Secure development life cycle includes memory-safety practices that can prevent double-free bugs.
Application security requirements can mandate memory-safety rules that reduce double-free risk.
Secure system architecture and engineering principles can prescribe safe memory-management patterns.
Secure coding standards directly address proper use of free() and similar functions.