Xorg server: A use-after-free flaw was found in the X.Org X server and Xwayland in miSyncDestroyFence(). (CVE-2026-50257)
0
MediumVulnerabilityCVE-2026-50257gcveosvubuntu-cve-2026-50257cve-2026-50257ubuntu-pro-14-04-ltsubuntu-pro-16-04-ltsubuntu-pro-18-04-ltsubuntu-pro-20-04-ltsubuntu-22-04-ltsubuntu-24-04-ltsubuntu-25-10ubuntu-26-10ubuntu-26-04-lts
Published: 06/05/2026 (06/05/2026, 12:16:00 UTC)
Source: GCVE Database
Product: xorg-server
Description
A use-after-free flaw was found in the X.Org X server and Xwayland in miSyncDestroyFence(). A client that sets up multiple fence triggers can trigger a use-after-free function pointer call. An attacker would connect to the X server to set up a fence and await that fence, then a second X connection destroys the fence, causing the use-after-free. This may be used to crash the server, or for privilege escalation if the X server runs as root.
CVSS v3.1
Score 7.8high
Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Affected software
xorg-server
pkg:deb/ubuntu/xorg-server?arch=source&distro=esm-infra-legacy/trustyAffected versions
=2:1.14.3-3ubuntu2=2:1.14.3-3ubuntu3=2:1.14.3-3ubuntu4=2:1.14.3-5ubuntu1=2:1.14.4-1ubuntu1=2:1.14.4-1ubuntu2=2:1.14.4.901-0ubuntu2=2:1.14.5-1ubuntu2=2:1.14.5-1ubuntu4=2:1.15.0-1ubuntu1=2:1.15.0-1ubuntu2=2:1.15.0-1ubuntu3=2:1.15.0-1ubuntu4=2:1.15.0-1ubuntu6=2:1.15.0-1ubuntu7=2:1.15.1-0ubuntu1=2:1.15.1-0ubuntu2=2:1.15.1-0ubuntu2.1=2:1.15.1-0ubuntu2.4=2:1.15.1-0ubuntu2.5=2:1.15.1-0ubuntu2.6=2:1.15.1-0ubuntu2.7=2:1.15.1-0ubuntu2.9=2:1.15.1-0ubuntu2.10=2:1.15.1-0ubuntu2.11=2:1.15.1-0ubuntu2.11+esm2=2:1.15.1-0ubuntu2.11+esm3=2:1.15.1-0ubuntu2.11+esm4=2:1.15.1-0ubuntu2.11+esm5=2:1.15.1-0ubuntu2.11+esm6=2:1.15.1-0ubuntu2.11+esm7=2:1.15.1-0ubuntu2.11+esm8=2:1.15.1-0ubuntu2.11+esm9=2:1.15.1-0ubuntu2.11+esm11=2:1.15.1-0ubuntu2.11+esm12
xorg-server
pkg:deb/ubuntu/xorg-server?arch=source&distro=esm-infra/xenialAffected versions
=2:1.17.2-1ubuntu9=2:1.17.2-1ubuntu10=2:1.17.3-2ubuntu1=2:1.17.3-2ubuntu2=2:1.17.3-2ubuntu3=2:1.17.3-2ubuntu4=2:1.18.1-1ubuntu3=2:1.18.1-1ubuntu4=2:1.18.3-1ubuntu1=2:1.18.3-1ubuntu2=2:1.18.3-1ubuntu2.2=2:1.18.3-1ubuntu2.3=2:1.18.4-0ubuntu0.1=2:1.18.4-0ubuntu0.2=2:1.18.4-0ubuntu0.3=2:1.18.4-0ubuntu0.4=2:1.18.4-0ubuntu0.6=2:1.18.4-0ubuntu0.7=2:1.18.4-0ubuntu0.8=2:1.18.4-0ubuntu0.9=2:1.18.4-0ubuntu0.10=2:1.18.4-0ubuntu0.11=2:1.18.4-0ubuntu0.12=2:1.18.4-0ubuntu0.12+esm1=2:1.18.4-0ubuntu0.12+esm2=2:1.18.4-0ubuntu0.12+esm4=2:1.18.4-0ubuntu0.12+esm5=2:1.18.4-0ubuntu0.12+esm6=2:1.18.4-0ubuntu0.12+esm8=2:1.18.4-0ubuntu0.12+esm9=2:1.18.4-0ubuntu0.12+esm10=2:1.18.4-0ubuntu0.12+esm12=2:1.18.4-0ubuntu0.12+esm13=2:1.18.4-0ubuntu0.12+esm14=2:1.18.4-0ubuntu0.12+esm15=2:1.18.4-0ubuntu0.12+esm16=2:1.18.4-0ubuntu0.12+esm17=2:1.18.4-0ubuntu0.12+esm18
xorg-server-hwe-16.04
pkg:deb/ubuntu/xorg-server-hwe-16.04?arch=source&distro=esm-infra/xenialAffected versions
=2:1.18.4-1ubuntu6.1~16.04.1=2:1.18.4-1ubuntu6.1~16.04.2=2:1.19.3-1ubuntu1~16.04.2=2:1.19.3-1ubuntu1~16.04.3=2:1.19.3-1ubuntu1~16.04.4=2:1.19.5-0ubuntu2~16.04.1=2:1.19.6-1ubuntu4~16.04.1=2:1.19.6-1ubuntu4.1~16.04.1=2:1.19.6-1ubuntu4.1~16.04.2=2:1.19.6-1ubuntu4.1~16.04.3=2:1.19.6-1ubuntu4.1~16.04.4=2:1.19.6-1ubuntu4.1~16.04.5=2:1.19.6-1ubuntu4.1~16.04.6=2:1.19.6-1ubuntu4.1~16.04.6+esm1=2:1.19.6-1ubuntu4.1~16.04.6+esm3=2:1.19.6-1ubuntu4.1~16.04.6+esm4=2:1.19.6-1ubuntu4.1~16.04.6+esm5=2:1.19.6-1ubuntu4.1~16.04.6+esm6=2:1.19.6-1ubuntu4.1~16.04.6+esm7=2:1.19.6-1ubuntu4.1~16.04.6+esm8=2:1.19.6-1ubuntu4.1~16.04.6+esm9=2:1.19.6-1ubuntu4.1~16.04.6+esm10
xorg-server
pkg:deb/ubuntu/xorg-server?arch=source&distro=esm-infra/bionicAffected versions
=2:1.19.5-0ubuntu2=2:1.19.6-1ubuntu1=2:1.19.6-1ubuntu2=2:1.19.6-1ubuntu3=2:1.19.6-1ubuntu4=2:1.19.6-1ubuntu4.1=2:1.19.6-1ubuntu4.2=2:1.19.6-1ubuntu4.3=2:1.19.6-1ubuntu4.4=2:1.19.6-1ubuntu4.5=2:1.19.6-1ubuntu4.6=2:1.19.6-1ubuntu4.7=2:1.19.6-1ubuntu4.8=2:1.19.6-1ubuntu4.9=2:1.19.6-1ubuntu4.10=2:1.19.6-1ubuntu4.11=2:1.19.6-1ubuntu4.12=2:1.19.6-1ubuntu4.13=2:1.19.6-1ubuntu4.14=2:1.19.6-1ubuntu4.15=2:1.19.6-1ubuntu4.15+esm1=2:1.19.6-1ubuntu4.15+esm3=2:1.19.6-1ubuntu4.15+esm4=2:1.19.6-1ubuntu4.15+esm5=2:1.19.6-1ubuntu4.15+esm7=2:1.19.6-1ubuntu4.15+esm8=2:1.19.6-1ubuntu4.15+esm9=2:1.19.6-1ubuntu4.15+esm10=2:1.19.6-1ubuntu4.15+esm11=2:1.19.6-1ubuntu4.15+esm12=2:1.19.6-1ubuntu4.15+esm13
xorg-server-hwe-18.04
pkg:deb/ubuntu/xorg-server-hwe-18.04?arch=source&distro=esm-infra/bionicAffected versions
=2:1.20.1-3ubuntu2.1~18.04.1=2:1.20.4-1ubuntu3~18.04.1=2:1.20.5+git20191008-0ubuntu1~18.04.1=2:1.20.8-2ubuntu2.1~18.04.1=2:1.20.8-2ubuntu2.2~18.04.1=2:1.20.8-2ubuntu2.2~18.04.2=2:1.20.8-2ubuntu2.2~18.04.3=2:1.20.8-2ubuntu2.2~18.04.4=2:1.20.8-2ubuntu2.2~18.04.5=2:1.20.8-2ubuntu2.2~18.04.6=2:1.20.8-2ubuntu2.2~18.04.7=2:1.20.8-2ubuntu2.2~18.04.8=2:1.20.8-2ubuntu2.2~18.04.9=2:1.20.8-2ubuntu2.2~18.04.10=2:1.20.8-2ubuntu2.2~18.04.11=2:1.20.8-2ubuntu2.2~18.04.11+esm1=2:1.20.8-2ubuntu2.2~18.04.11+esm2=2:1.20.8-2ubuntu2.2~18.04.11+esm3=2:1.20.8-2ubuntu2.2~18.04.11+esm4=2:1.20.8-2ubuntu2.2~18.04.11+esm5
xorg-server
pkg:deb/ubuntu/xorg-server?arch=source&distro=esm-infra/focalAffected versions
=2:1.20.5+git20191008-0ubuntu1=2:1.20.6-1ubuntu1=2:1.20.7-2ubuntu1=2:1.20.7-2ubuntu2=2:1.20.8-2ubuntu2=2:1.20.8-2ubuntu2.1=2:1.20.8-2ubuntu2.2=2:1.20.8-2ubuntu2.3=2:1.20.8-2ubuntu2.4=2:1.20.8-2ubuntu2.6=2:1.20.9-2ubuntu1.1~20.04.1=2:1.20.9-2ubuntu1.2~20.04.1=2:1.20.9-2ubuntu1.2~20.04.2=2:1.20.11-1ubuntu1~20.04.2=2:1.20.13-1ubuntu1~20.04.2=2:1.20.13-1ubuntu1~20.04.3=2:1.20.13-1ubuntu1~20.04.4=2:1.20.13-1ubuntu1~20.04.5=2:1.20.13-1ubuntu1~20.04.6=2:1.20.13-1ubuntu1~20.04.8=2:1.20.13-1ubuntu1~20.04.9=2:1.20.13-1ubuntu1~20.04.12=2:1.20.13-1ubuntu1~20.04.14=2:1.20.13-1ubuntu1~20.04.15=2:1.20.13-1ubuntu1~20.04.16=2:1.20.13-1ubuntu1~20.04.17=2:1.20.13-1ubuntu1~20.04.18=2:1.20.13-1ubuntu1~20.04.19=2:1.20.13-1ubuntu1~20.04.20=2:1.20.13-1ubuntu1~20.04.20+esm1
xorg-server
pkg:deb/ubuntu/xorg-server?arch=source&distro=jammyAffected versions
=2:1.20.13-1ubuntu1=2:1.20.13-1ubuntu2=2:1.20.14-1ubuntu1=2:21.1.3-2ubuntu2=2:21.1.3-2ubuntu2.1=2:21.1.3-2ubuntu2.2=2:21.1.3-2ubuntu2.3=2:21.1.3-2ubuntu2.4=2:21.1.3-2ubuntu2.5=2:21.1.3-2ubuntu2.6=2:21.1.3-2ubuntu2.7=2:21.1.3-2ubuntu2.8=2:21.1.3-2ubuntu2.9=2:21.1.4-2ubuntu1.7~22.04.1=2:21.1.4-2ubuntu1.7~22.04.2=2:21.1.4-2ubuntu1.7~22.04.5=2:21.1.4-2ubuntu1.7~22.04.7=2:21.1.4-2ubuntu1.7~22.04.8=2:21.1.4-2ubuntu1.7~22.04.9=2:21.1.4-2ubuntu1.7~22.04.10=2:21.1.4-2ubuntu1.7~22.04.11=2:21.1.4-2ubuntu1.7~22.04.12=2:21.1.4-2ubuntu1.7~22.04.13=2:21.1.4-2ubuntu1.7~22.04.14=2:21.1.4-2ubuntu1.7~22.04.15=2:21.1.4-2ubuntu1.7~22.04.16
xwayland
pkg:deb/ubuntu/xwayland?arch=source&distro=jammyAffected versions
=2:21.1.2-0ubuntu1=2:21.1.3-1=2:21.1.3-1ubuntu1=2:21.1.4-1=2:22.1.0-1=2:22.1.1-1=2:22.1.1-1ubuntu0.1=2:22.1.1-1ubuntu0.2=2:22.1.1-1ubuntu0.3=2:22.1.1-1ubuntu0.4=2:22.1.1-1ubuntu0.5=2:22.1.1-1ubuntu0.6=2:22.1.1-1ubuntu0.7=2:22.1.1-1ubuntu0.9=2:22.1.1-1ubuntu0.10=2:22.1.1-1ubuntu0.11=2:22.1.1-1ubuntu0.12=2:22.1.1-1ubuntu0.13=2:22.1.1-1ubuntu0.14=2:22.1.1-1ubuntu0.15=2:22.1.1-1ubuntu0.17=2:22.1.1-1ubuntu0.18=2:22.1.1-1ubuntu0.19=2:22.1.1-1ubuntu0.20
xorg-server
pkg:deb/ubuntu/xorg-server?arch=source&distro=nobleAffected versions
=2:21.1.7-3ubuntu2=2:21.1.7-3ubuntu2.1=2:21.1.10-1ubuntu1=2:21.1.11-2ubuntu1=2:21.1.12-1ubuntu1=2:21.1.12-1ubuntu1.1=2:21.1.12-1ubuntu1.2=2:21.1.12-1ubuntu1.3=2:21.1.12-1ubuntu1.4=2:21.1.12-1ubuntu1.5=2:21.1.12-1ubuntu1.6=2:21.1.12-1ubuntu1.8
xwayland
pkg:deb/ubuntu/xwayland?arch=source&distro=nobleAffected versions
=2:23.2.0-1=2:23.2.0-1ubuntu0.1=2:23.2.3-1=2:23.2.4-1=2:23.2.4-1build1=2:23.2.4-1build2=2:23.2.4-1build3=2:23.2.6-1=2:23.2.6-1ubuntu0.1=2:23.2.6-1ubuntu0.2=2:23.2.6-1ubuntu0.4=2:23.2.6-1ubuntu0.5=2:23.2.6-1ubuntu0.6=2:23.2.6-1ubuntu0.7=2:23.2.6-1ubuntu0.8
xorg-server
pkg:deb/ubuntu/xorg-server?arch=source&distro=questingAffected versions
=2:21.1.16-1ubuntu1=2:21.1.18-1ubuntu1=2:21.1.18-1ubuntu1.1
xwayland
pkg:deb/ubuntu/xwayland?arch=source&distro=questingAffected versions
=2:24.1.6-1=2:24.1.6-1ubuntu1=2:24.1.6-1ubuntu1.1
xorg-server
pkg:deb/ubuntu/xorg-server?arch=source&distro=stonkingAffected versions
=2:21.1.22-1ubuntu1=2:21.1.22-1ubuntu4=2:21.1.24-1ubuntu1
xwayland
pkg:deb/ubuntu/xwayland?arch=source&distro=stonkingAffected versions
=2:24.1.10-1=2:24.1.12-1=2:24.1.13-1=2:24.1.14-1
xorg-server
pkg:deb/ubuntu/xorg-server?arch=source&distro=resoluteAffected versions
=2:21.1.18-1ubuntu1=2:21.1.21-1ubuntu1=2:21.1.22-1ubuntu1=2:21.1.22-1ubuntu1.2
xwayland
pkg:deb/ubuntu/xwayland?arch=source&distro=resoluteAffected versions
=2:24.1.6-1ubuntu1=2:24.1.8-1=2:24.1.9-1=2:24.1.10-1
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Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- UBUNTU-CVE-2026-50257
- Osv Schema Version
- 1.7.0
- Ecosystems
- ["Ubuntu:Pro:14.04:LTS","Ubuntu:Pro:16.04:LTS","Ubuntu:Pro:18.04:LTS","Ubuntu:Pro:20.04:LTS","Ubuntu:22.04:LTS","Ubuntu:24.04:LTS","Ubuntu:25.10","Ubuntu:26.10","Ubuntu:26.04:LTS"]
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6ad3f6102cdf04f656664123
Added to database: 10/17/2026, 22:26:24 UTC
Last updated: 10/18/2026, 02:05:36 UTC
Views: 3
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