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High severity7.8NVD Advisory· Published Jun 5, 2026· Updated Jun 5, 2026

CVE-2026-50258

CVE-2026-50258

Description

X.Org X server and Xwayland stack buffer overflow due to unchecked key types, potentially leading to crashes or privilege escalation.

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

X.Org X server and Xwayland stack buffer overflow due to unchecked key types, potentially leading to crashes or privilege escalation.

Vulnerability

A stack-based buffer overflow flaw exists in the X.Org X server and Xwayland due to the CheckKeyTypes() function not verifying or clamping non-canonical key types to XkbMaxShiftLevel. This allows a client to set key types to excessive shift levels, triggering stack overflows. This vulnerability is an incomplete fix for CVE-2025-26597. Affected versions include xorg-x11-server up to 21.1.22 and xorg-x11-server-Xwayland up to 24.1.9 [3].

Exploitation

An attacker with the ability to connect to the X server as a client can trigger this vulnerability. By changing key types to excessive shift levels, the attacker can cause stack overflows. This requires no special privileges beyond the ability to connect to the X server [3].

Impact

Successful exploitation of this vulnerability can lead to a denial-of-service by crashing the X server. Furthermore, if the X server is running with root privileges, this flaw may be exploited for privilege escalation [3].

Mitigation

This issue has been fixed upstream in xorg-server version 21.1.23 and xwayland version 24.1.12. The fix can be found at [4]. No workarounds are mentioned in the available references, and the vulnerability is not listed as being part of the KEV catalog at this time.

References
  1. stack buffer overflow in XKB key types due to unchecked shift levels
  2. Making sure you're not a bot!

AI Insight generated on Jun 5, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.

Affected products

4

Patches

0

No patches discovered yet.

Vulnerability mechanics

No source-code context for this CVE — mechanics is only generated when we can read the actual fix diff. Without that, the four sections (root cause, attack vector, affected code, fix) would be speculation rather than analysis.

References

5

News mentions

0

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