CVE-2026-55653
Publication date 23 June 2026
Last updated 26 June 2026
Ubuntu priority
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).
Status
| Package | Ubuntu Release | Status |
|---|---|---|
| openssh | 26.04 LTS resolute |
Needs evaluation
|
| 25.10 questing |
Needs evaluation
|
|
| 24.04 LTS noble |
Needs evaluation
|
|
| 22.04 LTS jammy |
Needs evaluation
|
|
| 20.04 LTS focal |
Needs evaluation
|
|
| 18.04 LTS bionic |
Needs evaluation
|
|
| 16.04 LTS xenial |
Needs evaluation
|
|
| 14.04 LTS trusty |
Needs evaluation
|
|
| openssh-ssh1 | 26.04 LTS resolute | Ignored |
| 25.10 questing | Ignored | |
| 24.04 LTS noble | Ignored | |
| 22.04 LTS jammy | Ignored | |
| 20.04 LTS focal | Ignored | |
| 18.04 LTS bionic | Ignored |
Notes
mdeslaur
openssh-ssh1 is only provided for compatibility with old devices that cannot be upgraded to modern protocols. We will not be providing any security support for the openssh-ssh1 package as it is insecure and should be used in trusted environments only.
Severity score breakdown
CVSS version: CVSS v3.0
Base score
4.3 · Medium
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L