Vulnerability in OpenBSD OpenSSH
CVE-2026-55655
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.0 (Medium). Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:L/A:N.
EPSS exploit prediction
EPSS: 0.001 (1.8th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 2nd percentile — 1.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.001 · newest: 0.001 · change: +0.000
Affected products
- OpenBSD OpenSSH
- Red Hat Enterprise Linux 10 — versions 0:9.9p1-25.el10_2
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 8 — versions 0:8.0p1-30.el8_10
- Red Hat Enterprise Linux 9 — versions 0:9.9p1-9.el9_8
- Red Hat Hardened Images — versions 10.3p1-6.hum1
- Red Hat Openshift Container Platform 4
- Red Hat Update Infrastructure 5 — versions 1786435483, 1786533529
- Red Hat Enterprise Linux — versions 6.0, 7.0, 8.0
Weakness classification (CWE)
References
- access.redhat.com/security/cve/CVE-2026-55655 (vdb-entry, Vendor Advisory)
- bugzilla.redhat.com/show_bug.cgi (issue-tracking, Issue Tracking, Vendor Advisory)
- access.redhat.com/errata/RHSA-2026:36759 (vendor-advisory)
- access.redhat.com/errata/RHSA-2026:47755 (vendor-advisory)
- access.redhat.com/errata/RHSA-2026:47756 (vendor-advisory)
- access.redhat.com/errata/RHSA-2026:47757 (vendor-advisory)
- access.redhat.com/errata/RHSA-2026:54387 (vendor-advisory)
- access.redhat.com/errata/RHSA-2026:58981 (vendor-advisory)
Frequently asked questions
- What is CVE-2026-55655?
- CVE-2026-55655 is a medium-severity vulnerability in OpenBSD OpenSSH, classified under CWE-923. CVSS score: 5.0/10. Published 2026-06-23.
- How severe is CVE-2026-55655?
- Medium severity. CVSS v3 base score is 5.0 out of 10.