CVE intelligence

CVE-2026-50258

Vulnerability intelligence

Published Jun 5, 2026Sources checked Nov 13, 2026

7.8HIGHCVSS out of 10

What this means

Review the available evidence

CVE-2026-50258 and is rated High severity with a CVSS score of 7.8. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.

What to do next

Remediation and response

Microsoft Security Response Center guidance

Vendor revision: Jun 11, 2026

CBL-Mariner Releases

Vendor-listed releases

24.1.12-1

CISA KEVNot listedBased on the latest collected catalog

EPSS0.2%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors0Source-linked actor relationships

Overview

What is CVE-2026-50258?

A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland. The X server has multiple stack buffers sized XkbMaxShiftLevel * XkbNumKbdGroups but CheckKeyTypes() does not verify or clamp non-canonical key types to XkbMaxShiftLevel.

A client can change key types to excessive shift levels and trigger stack overflows. This is caused by an incomplete fix of CVE-2025-26597.

This may be used to crash the server, or for privilege escalation if the X server runs as root.

Source: NVD