Stack Buffer Overflow in X.Org X Server (_XkbSetMapChecks)
CVE-2026-50259 Published on June 5, 2026

Xorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: stack buffer overflow in xkb setmap request via mapwidths indexing
A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland. _XkbSetMapChecks() declares a fixed-size stack buffer mapWidths[256] indexed by key type index. The helper function CheckKeyTypes() writes to this buffer at a client-controlled offset, allowing a stack buffer overflow. This may be used to crash the server, or for privilege escalation if the X server runs as root.

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Vulnerability Analysis

CVE-2026-50259 can be exploited with local system access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to be very high.

Attack Vector:
LOCAL
Attack Complexity:
LOW
Privileges Required:
LOW
User Interaction:
NONE
Scope:
UNCHANGED
Confidentiality Impact:
HIGH
Integrity Impact:
HIGH
Availability Impact:
HIGH

Timeline

Reported to Red Hat.

Made public. 18 days later.

Weakness Type

What is a Stack Overflow Vulnerability?

A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).

CVE-2026-50259 has been classified to as a Stack Overflow vulnerability or weakness.


Products Associated with CVE-2026-50259

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Red Hat Enterprise Linux (RHEL)
 
Red Hat Rhel E4s
 
Red Hat Rhel Els
 
Red Hat Rhel Eus
 
Red Hat Rhel Aus
 
Red Hat Rhel Eus Long Life
 
Red Hat Enterprise Linux Eus
 
Red Hat Rhel Tus
 

Affected Versions

Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10.0 Extended Update Support: Red Hat Enterprise Linux 7 Extended Lifecycle Support: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support: Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On: Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support: Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On: Red Hat Enterprise Linux 8.8 Telecommunications Update Service: Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions: Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions: Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions: Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions: Red Hat Enterprise Linux 9.6 Extended Update Support: Red Hat Enterprise Linux 9.6 Extended Update Support: Red Hat Enterprise Linux 6: Red Hat Enterprise Linux 6: Red Hat Enterprise Linux 7: Red Hat Enterprise Linux Server (v. 7 ELS): Red Hat Enterprise Linux Server Optional (v. 7 ELS): Red Hat Enterprise Linux AppStream EUS (v. 10.0): Red Hat Enterprise Linux AppStream (v. 10): Red Hat Enterprise Linux AppStream (v. 8): Red Hat Enterprise Linux AppStream AUS (v.8.4): Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4): Red Hat Enterprise Linux AppStream AUS (v.8.6): Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6): Red Hat Enterprise Linux AppStream E4S (v.8.8): Red Hat Enterprise Linux AppStream TUS (v.8.8): Red Hat Enterprise Linux AppStream E4S (v.9.2): Red Hat Enterprise Linux AppStream E4S (v.9.4): Red Hat Enterprise Linux AppStream EUS (v.9.6): Red Hat Enterprise Linux AppStream (v. 9): Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0): Red Hat Enterprise Linux CodeReady Linux Builder (v. 10): Red Hat Enterprise Linux CRB (v. 8): Red Hat CodeReady Linux Builder EUS (v.9.6): Red Hat Enterprise Linux CodeReady Linux Builder (v. 9): Red Hat Enterprise Linux 6: Red Hat Enterprise Linux 7:

Exploit Probability

EPSS
0.22%
Percentile
11.90%

EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.