---
id: CVE-2025-26601
title: A use-after-free flaw was found in X.Org and Xwayland
summary: >-
  A use-after-free flaw was found in X.Org and Xwayland. When changing an alarm,
  the values of the change mask are evaluated one after the other, changing the
  trigger values as requested, and eventually, SyncInitTrigger() is called. If
  one…
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-416
  - CWE-416
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-2025-26601'
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-2025-26601'
    label: secalert@redhat.com
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2345251'
    label: secalert@redhat.com
  - url: 'https://lists.debian.org/debian-lts-announce/2025/02/msg00036.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://security.netapp.com/advisory/ntap-20250516-0004/'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.00393
epssPercentile: 0.30683
ingestedAt: '2026-06-29T13:24:34.172Z'
---

## Overview

A use-after-free flaw was found in X.Org and Xwayland. When changing an alarm, the values of the change mask are evaluated one after the other, changing the trigger values as requested, and eventually, SyncInitTrigger() is called. If one of the changes triggers an error, the function will return early, not adding the new sync object, possibly causing a use-after-free when the alarm eventually triggers.

## 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`