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CVE-2026-50258: Xorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: stack buffer overflow in xkb key types due to unchecked shift levels

highCVSS 7.8CVE-2026-50258

CSIRTS triage

vendor: Xorgproduct: xorg-x11-serverOther
What
There is a stack buffer overflow in xkb key types due to unchecked shift levels.
Who is affected
Deployments of xorg-x11-server.
Urgency
Remediation is urgent due to the high severity and potential for exploitation.
Action
Update to the latest version of xorg-x11-server.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source
Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity
high — CVSS 7.8
Published
2026-06-09
Exploitation
Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50258

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Referenced CVEs

CVECSIRTS overviewExternal
CVE-2026-50258coverage & exploitation statusNVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for Xorg-x11-server

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

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