CVE-2026-55655: openbsd openssh
Vulnerability summary
CVE-2026-55655 is a medium (CVSS 6.1) vulnerability in openbsd openssh. EPSS estimates a 0.14% chance of exploitation in the next 30 days, higher than 2.8% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 8Timeline
- 23-06-2026PublishedVulnerability first disclosed.
- 14-10-2026Last modifiedVulnerability information updated.
Description
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.
CVSS metrics
4 scores · 4 sources · 1 version- CVE.orgCNA5.0MediumCVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:L/A:NDiffers
- OSV · UbuntuEcosystem advisory · calculated6.1MediumCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N
- OSV · DebianEcosystem advisory · calculated6.1MediumCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N
EPSS trend
Probability
0.14%
Chance of exploitation in the next 30 days
Percentile
3%
Versus all other CVEs
30-day change
+0.05 pp
From 0.09% on 19-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Ubuntu2 products
- opensshAll versions (No fix recorded)
- openssh-ssh1All versions (No fix recorded)
Debian1 product
- opensshAll versions (No fix recorded)
Openbsd1 product
- opensshna
Redhat1 product
- enterprise_linuxEOL6.0 | 7.0 | 8.0 | 9.0 | 10.0
4 vendors · 5 products
