---
id: CVE-2025-26595
title: A buffer overflow flaw was found in X.Org and Xwayland
summary: >-
  A buffer overflow flaw was found in X.Org and Xwayland. The code in
  XkbVModMaskText() allocates a fixed-sized buffer on the stack and copies the
  names of the virtual modifiers to that buffer. The code fails to check the
  bounds of the buf…
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-121
  - 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-2025-26595'
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-2025-26595'
    label: secalert@redhat.com
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2345257'
    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: 0.35423
ingestedAt: '2026-06-29T13:24:34.166Z'
---

## Overview

A buffer overflow flaw was found in X.Org and Xwayland. The code in XkbVModMaskText() allocates a fixed-sized buffer on the stack and copies the names of the virtual modifiers to that buffer. The code fails to check the bounds of the buffer and would copy the data regardless of the size.

## 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`