Is CVE-2026-50257 in the CISA KEV catalog?

No. CVE-2026-50257 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-50257?

CVE-2026-50257 has a CVSS v3 base score of 6.6 (Moderate).

What is the EPSS score for CVE-2026-50257?

CVE-2026-50257 has an EPSS score of 0.14% (4th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-50257?

Upgrade xorg-server on debian 13 to 2:21.1.16-1.3+deb13u3 or later. Fixes are available for 65 affected products.

CVE & CISA-KEV Catalog

CVE-2026-50257

MEDIUM

6.6

CVSS v3

NVD

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.

CWE-416Use After Free

How to fix

Remediation Available

xorg-serverDebian

Fixed in:2:21.1.16-1.3+deb13u3CVE-2026-50257

Fixed in:2:21.1.23-1CVE-2026-50257

tigervncRed Hat / RHEL

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

tigervncRocky

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

tigervnc-debuginfoRocky

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

tigervnc-debuginfoRed Hat / RHEL

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

tigervnc-debugsourceRed Hat / RHEL

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

tigervnc-debugsourceRocky

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

tigervnc-iconsRocky

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

tigervnc-iconsRed Hat / RHEL

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

tigervnc-licenseRocky

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

tigervnc-licenseRed Hat / RHEL

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

tigervnc-selinuxRocky

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

tigervnc-selinuxRed Hat / RHEL

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

tigervnc-serverRed Hat / RHEL

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

tigervnc-serverRocky

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

tigervnc-server-debuginfoRocky

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

tigervnc-server-debuginfoRed Hat / RHEL

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

tigervnc-server-minimalRocky

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

tigervnc-server-minimalRed Hat / RHEL

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

tigervnc-server-minimal-debuginfoRocky

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

tigervnc-server-minimal-debuginfoRed Hat / RHEL

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

tigervnc-server-moduleRed Hat / RHEL

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

tigervnc-server-moduleRocky

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

tigervnc-server-module-debuginfoRed Hat / RHEL

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

tigervnc-server-module-debuginfoRocky

Fixed in:0:1.15.0-10.el8_10RHSA-2026:28923

Fixed in:0:1.15.0-7.el9_8.2RHSA-2026:29844

xorg-x11-serverRocky

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-serverRed Hat / RHEL

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-XdmxRed Hat / RHEL

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-XdmxRocky

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-Xdmx-debuginfoRocky

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-Xdmx-debuginfoRed Hat / RHEL

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-XephyrRed Hat / RHEL

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-XephyrRocky

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-Xephyr-debuginfoRed Hat / RHEL

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-Xephyr-debuginfoRocky

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-XnestRed Hat / RHEL

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-XnestRocky

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-Xnest-debuginfoRed Hat / RHEL

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-Xnest-debuginfoRocky

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-XorgRocky

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-XorgRed Hat / RHEL

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-Xorg-debuginfoRed Hat / RHEL

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-Xorg-debuginfoRocky

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-XvfbRocky

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-XvfbRed Hat / RHEL

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-Xvfb-debuginfoRed Hat / RHEL

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-Xvfb-debuginfoRocky

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-XwaylandRed Hat / RHEL

Fixed in:0:24.1.9-4.el10_2.2RHSA-2026:26566

Fixed in:0:21.1.3-20.el8_10.2RHSA-2026:26562

Fixed in:0:24.1.9-4.el9_8.2RHSA-2026:26590

xorg-x11-server-XwaylandRocky

Fixed in:0:24.1.9-4.el10_2.2RHSA-2026:26566

Fixed in:0:21.1.3-20.el8_10.2RHSA-2026:26562

Fixed in:0:24.1.9-4.el9_8.2RHSA-2026:26590

xorg-x11-server-Xwayland-debuginfoRocky

Fixed in:0:24.1.9-4.el10_2.2RHSA-2026:26566

Fixed in:0:21.1.3-20.el8_10.2RHSA-2026:26562

Fixed in:0:24.1.9-4.el9_8.2RHSA-2026:26590

xorg-x11-server-Xwayland-debuginfoRed Hat / RHEL

Fixed in:0:24.1.9-4.el10_2.2RHSA-2026:26566

Fixed in:0:21.1.3-20.el8_10.2RHSA-2026:26562

Fixed in:0:24.1.9-4.el9_8.2RHSA-2026:26590

xorg-x11-server-Xwayland-debugsourceRocky

Fixed in:0:24.1.9-4.el10_2.2RHSA-2026:26566

Fixed in:0:21.1.3-20.el8_10.2RHSA-2026:26562

Fixed in:0:24.1.9-4.el9_8.2RHSA-2026:26590

xorg-x11-server-Xwayland-debugsourceRed Hat / RHEL

Fixed in:0:24.1.9-4.el10_2.2RHSA-2026:26566

Fixed in:0:21.1.3-20.el8_10.2RHSA-2026:26562

Fixed in:0:24.1.9-4.el9_8.2RHSA-2026:26590

xorg-x11-server-Xwayland-develRed Hat / RHEL

Fixed in:0:24.1.9-4.el10_2.2RHSA-2026:26566

Fixed in:0:24.1.9-4.el9_8.2RHSA-2026:26590

xorg-x11-server-Xwayland-develRocky

Fixed in:0:24.1.9-4.el10_2.2RHSA-2026:26566

Fixed in:0:24.1.9-4.el9_8.2RHSA-2026:26590

xorg-x11-server-commonRocky

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-commonRed Hat / RHEL

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-debuginfoRocky

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-debuginfoRed Hat / RHEL

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-debugsourceRocky

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-debugsourceRed Hat / RHEL

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-develRed Hat / RHEL

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-develRocky

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-sourceRed Hat / RHEL

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

xorg-x11-server-sourceRocky

Fixed in:0:1.20.11-28.el8_10.2RHSA-2026:26709

Fixed in:0:1.20.11-34.el9_8.2RHSA-2026:26610

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorLocal

Attack ComplexityLow

Privileges RequiredLow

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityLow

IntegrityLow

AvailabilityHigh

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H/E:U

Exploit Intelligence

0.14%probability of exploitation in 30 days

4thpercentile

Low risk: more likely to be exploited than 4% of all known CVEs.

References

Patch1

gitlab.freedesktop.org

Third-Party Advisory3

Other references9

Related Vulnerabilities

Other CWE-416 (Use After Free) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2019-0708	Critical	9.8	100%	KEV + Ransom	-
CVE-2021-31166	Critical	9.8	100%	KEV	Fix
CVE-2015-5119	Critical	9.8	99%	KEV	-
CVE-2010-3962	High	8.1	97%	KEV	-
CVE-2015-0313	Critical	9.8	96%	KEV	Fix
CVE-2017-9798	High	7.5	95%	-	Fix

Embed a live status badge for CVE-2026-50257

Markdown

[![CVE-2026-50257](https://tridentstack.com/cve/badge/CVE-2026-50257.svg)](https://tridentstack.com/cve/CVE-2026-50257)

HTML

<a href="https://tridentstack.com/cve/CVE-2026-50257"><img src="https://tridentstack.com/cve/badge/CVE-2026-50257.svg" alt="CVE-2026-50257"></a>

Find and fix vulnerabilities across your fleet

TridentStack Control continuously scans your Windows, macOS, and Linux fleet for known vulnerabilities, prioritizes them by severity and active exploitation, and patches them automatically.

Start free

This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-06-30.