X.Org Server and XWayland: Heap buffer overflow in XKB
Summary
A heap buffer overflow in the X Keyboard Extension (XKB) of the X.Org X server and XWayland allows an authenticated X client to crash the X server or potentially execute code in its context. The cause is mismatching size calculations between XkbAllocNames and ChangeKeycodeRange. Exploitation requires a local, authenticated X client session; the vector is local with low complexity and low privileges.
Affected
- xorg-server (X.Org X server): before 21.1.25
- XWayland: before 24.1.14
- Distribution packages: affected versions vary, check your vendor advisories.
Fixed in
- xorg-server 21.1.25
- XWayland 24.1.14
- Distribution packages: exact fixed package versions unknown; check your distribution's advisories.
Workaround
- No workaround is documented in the sources. Upgrading is the only remedy referenced.
- Where X11 or XWayland is not needed, remove the packages.
- On shared hosts, limit who has local interactive sessions.
Exploitation
- Not listed in CISA KEV.
- OffSeq reports it as not known to be exploited, with no public Nuclei template and no weaponisation evidence.
- No public proof of concept found as of 1 Nov 2026. EPSS: 0.2%.
Our recommendation
- Update xorg-server to 21.1.25 or XWayland to 24.1.14, or the distribution equivalent, in the next regular update cycle.
- Raise the priority to high on Linux desktops, shared terminal servers, jump hosts or systems using X11 forwarding.
- Check whether X or XWayland packages are installed, including on headless servers.
- Monitor for unexpected X server crashes.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- X.Org upstream fix commit gitlab.freedesktop.org
- X.Org Security Advisories www.x.org
- GamingOnLinux: xorg-server 21.1.25 and XWayland 24.1.14 released www.gamingonlinux.com
- Red Hat Errata RHSA-2026:85191 access.redhat.com
- OpenCVE: CVE-2026-93520 app.opencve.io
- Help Net Security: X.Org server fixed vulnerabilities www.helpnetsecurity.com
- Linux Security: Xorg and XWayland security fixes linuxsecurity.com
- OffSeq Radar: CVE-2026-93520 radar.offseq.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 1 Nov 2026, 21:54.
Original description (NVD)
A heap buffer overflow caused by mismatching size calculations between XkbAllocNames and ChangeKeycodeRange in X.org X server before 2.1.25 and XWayland before 24.1.14 could be used by authenticated X clients to crash or potentially execute code in X server context.
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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