CVE-2026-55655
MEDIUMDescription
A flaw was found in OpenSSH. A local unprivileged attacker on a Linux client host can hijack client-side X11 forwarding connections. This is possible by pre-binding the preferred abstract X socket name when X11 forwarding is enabled and a local UNIX-domain X socket is used. A successful attack can compromise the confidentiality of forwarded X11 traffic, including sensitive window contents and input, and may allow some manipulation of the forwarded session.
How to fix
This vulnerability affects an unusually large number of packages. The highest-confidence fixes are shown above; the full list is longer. Check the referenced advisories for complete coverage.
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:L/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 0% of all known CVEs.
References
Related Vulnerabilities
Other CWE-923 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2024-24974 | High | 7.5 | 9.8% | - | Fix |
| CVE-2025-48999 | High | 8.8 | 8.3% | - | Fix |
| CVE-2021-38487 | High | 8.2 | 3.3% | - | Fix |
| CVE-2022-2663 | Medium | 5.3 | 3.2% | - | Fix |
| CVE-2019-17440 | Critical | 10.0 | 1.7% | - | - |
| CVE-2021-32635 | Medium | 6.3 | 1.4% | - | - |
Common questions
How do I fix CVE-2026-55655?
Published advisories record a fix for 50 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2026-55655 being actively exploited?
Not that we know of. CVE-2026-55655 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.09% is the estimated probability that it will be exploited in the next 30 days. That is higher than 0% of all scored CVEs.
How severe is CVE-2026-55655?
CVE-2026-55655 has a CVSS v3 base score of 5.0, rated moderate. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-55655 affect?
Published advisories record a fix for openssh (Red Hat / RHEL), openssh (Rocky), openssh-askpass (Rocky), openssh-askpass (Red Hat / RHEL), and 46 more. Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-08-25.