EUVD-2026-38412
GHSA-28f3-55mq-pp68
Severity by source
AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Network-delivered via malicious server (AV:N), no privileges needed on attacker side (PR:N), but victim must initiate the connection (UI:R); impact is client-process termination only (A:L), no C or I impact.
Primary rating from Vendor (redhat).
CVSS VectorNVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Lifecycle Timeline
3DescriptionNVD
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).
AnalysisAI
Client-side Denial of Service in OpenSSH's Diffie-Hellman Group Exchange implementation allows a malicious SSH server to crash connecting clients running in FIPS mode. When a victim initiates an SSH connection to an attacker-controlled server, the server sends crafted DH-GEX group parameters that trigger a double free (CWE-415) during FIPS known-group validation, terminating the client process. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires two simultaneous conditions: (1) the OpenSSH client must be operating in FIPS mode - this is a non-default configuration typically enforced via system-wide FIPS policy (e.g., 'fips-mode-setup --enable' on RHEL) and is not present in standard installations; and (2) the victim user must actively initiate an SSH connection (UI:R) to a server controlled by the attacker. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 base score of 4.3 (Medium) reflects an availability-only impact limited to the client process (A:L, S:U), with no confidentiality or integrity consequences. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker operating a malicious SSH server on the internet (or on an internal network via server compromise or ARP poisoning) waits for a victim on a FIPS-mode RHEL or OpenShift system to initiate an SSH connection. When the victim's OpenSSH client begins the DH-GEX key exchange, the malicious server returns specially crafted group parameters that trigger the double free during FIPS known-group validation, causing the client process to crash and aborting the session. … |
| Remediation | No specific patched version of OpenSSH or Red Hat package has been identified in the available data; administrators should monitor https://access.redhat.com/security/cve/CVE-2026-55653 for errata as Red Hat releases fixes. … Detailed patch versions, workarounds, and compensating controls in full report. |
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Same weakness CWE-415 – Double Free
View allSame technique Denial Of Service
View allVendor StatusVendor
Debian
| Release | Status | Fixed Version | Urgency |
|---|---|---|---|
| bullseye | undetermined | 1:8.4p1-5+deb11u3 | - |
| bullseye (security) | undetermined | 1:8.4p1-5+deb11u7 | - |
| bookworm | undetermined | 1:9.2p1-2+deb12u10 | - |
| bookworm (security) | undetermined | 1:9.2p1-2+deb12u9 | - |
| trixie | undetermined | 1:10.0p1-7+deb13u4 | - |
| trixie (security) | undetermined | 1:10.0p1-7+deb13u2 | - |
| forky, sid | undetermined | 1:10.3p1-4 | - |
| (unstable) | fixed | undetermined | - |
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