---
id: CVE-2025-26596
title: A heap overflow flaw was found in X.Org and Xwayland
summary: >-
  A heap overflow flaw was found in X.Org and Xwayland. The computation of the
  length in XkbSizeKeySyms() differs from what is written in XkbWriteKeySyms(),
  which may lead to a heap-based buffer overflow.
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-787
  - CWE-787
vendor: tigervnc
product: tigervnc
affected:
  - tigervnc
  - x_server < 21.1.16
  - xwayland < 24.1.6
  - enterprise_linux = 7.0
  - enterprise_linux = 8.0
  - enterprise_linux = 9.0
patched:
  - x_server 21.1.16
  - xwayland 24.1.6
published: '2025-02-25'
updated: '2026-06-25'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-26596'
references:
  - url: 'https://access.redhat.com/errata/RHSA-2025:2500'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2025:2502'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2025:2861'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2025:2862'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2025:2865'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2025:2866'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2025:2873'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2025:2874'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2025:2875'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2025:2879'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2025:2880'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2025:3976'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2025:7163'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2025:7165'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2025:7458'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/security/cve/CVE-2025-26596'
    label: secalert@redhat.com
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2345256'
    label: secalert@redhat.com
  - url: 'https://lists.debian.org/debian-lts-announce/2025/02/msg00036.html'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.00438
epssPercentile: 0.37498
ingestedAt: '2026-06-29T13:24:34.167Z'
---

## Overview

A heap overflow flaw was found in X.Org and Xwayland. The computation of the length in XkbSizeKeySyms() differs from what is written in XkbWriteKeySyms(), which may lead to a heap-based buffer overflow.

## Affected

- `tigervnc`
- `x_server < 21.1.16`
- `xwayland < 24.1.6`
- `enterprise_linux = 7.0`
- `enterprise_linux = 8.0`
- `enterprise_linux = 9.0`

## Remediation

Upgrade past the affected range:

- `x_server 21.1.16`
- `xwayland 24.1.6`