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CVE Vulnerabilities

CVE-2026-50258

Stack-based Buffer Overflow

Published: Jun 05, 2026 | Modified: Jun 25, 2026
CVSS 3.x
N/A
Source:
NVD
CVSS 2.x
RedHat/V2
RedHat/V3
7.8 IMPORTANT
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Ubuntu
MEDIUM
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Additional information
NVDhttps://nvd.nist.gov/vuln/detail/CVE-2026-50258
CWEhttps://cwe.mitre.org/data/definitions/121.html

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.

Weakness

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).

Affected Software

NameVendorStart VersionEnd Version
X_serverX.org*21.1.23 (excluding)
XwaylandX.org*24.1.12 (excluding)
Enterprise_linuxRedhat7.0 (including)7.0 (including)
Enterprise_linuxRedhat8.0 (including)8.0 (including)
Enterprise_linuxRedhat9.0 (including)9.0 (including)
Enterprise_linuxRedhat10.0 (including)10.0 (including)
Red Hat Enterprise Linux 10RedHatxorg-x11-server-Xwayland-0:24.1.9-4.el10_2.2*
Red Hat Enterprise Linux 8RedHatxorg-x11-server-Xwayland-0:21.1.3-20.el8_10.2*
Red Hat Enterprise Linux 8RedHatxorg-x11-server-0:1.20.11-28.el8_10.2*
Red Hat Enterprise Linux 8RedHattigervnc-0:1.15.0-10.el8_10*
Red Hat Enterprise Linux 9RedHatxorg-x11-server-Xwayland-0:24.1.9-4.el9_8.2*
Red Hat Enterprise Linux 9RedHatxorg-x11-server-0:1.20.11-34.el9_8.2*
Red Hat Enterprise Linux 9RedHattigervnc-0:1.15.0-7.el9_8.2*
XwaylandUbuntuupstream*

Potential Mitigations

  • Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking.
  • D3-SFCV (Stack Frame Canary Validation) from D3FEND [REF-1334] discusses canary-based detection in detail.
  • Run or compile the software using features or extensions that randomly arrange the positions of a program’s executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.
  • Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as “rebasing” (for Windows) and “prelinking” (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.
  • For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].

References

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