CVE-2026-50257
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.
Key facts
- CVSS score
- 7.8 (v3.1)
- Severity
- HIGH
- CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H- Weakness (CWE)
- CWE-416
- EPSS score
- 0.2% (9th percentile)
- In CISA KEV
- No
- In EU EUVD
- Yes (EUVD-2026-34812)
- Published
- June 5, 2026
- NVD last modified
- August 5, 2026
- Status
- Modified
EU Vulnerability Database (EUVD)
This vulnerability is also tracked by ENISA as EUVD-2026-34812 in the EU Vulnerability Database. Last updated in EUVD on September 28, 2026.
View on the EU Vulnerability DatabaseAffected products
- redhat / enterprise linux
- redhat / enterprise linux
- redhat / enterprise linux
- redhat / enterprise linux
- x.org / x server
- x.org / xwayland
Certified products that may be affected
31 FIPS 140 or Common Criteria certified products, from automated matching by sec-certs.org.
- Red Hat Enterprise Linux 8 NSS Cryptographic Module - Red Hat, Inc. - FIPS 140 5513 - active
- Red Hat Enterprise Linux 8 Kernel Cryptographic API - Red Hat, LLC - FIPS 140 5461 - active
- Red Hat Enterprise Linux 9 Kernel Cryptographic API - Red Hat, Inc. - FIPS 140 5445 - active
- Red Hat Enterprise Linux 9 libgcrypt - Red Hat, Inc. - FIPS 140 5366 - active
- Red Hat Enterprise Linux 8 Kernel Cryptographic API - Red Hat, Inc. - FIPS 140 5089 - active
See all 31 in the Security Certifications Explorer.
References
- https://access.redhat.com/errata/RHSA-2026:26562
- https://access.redhat.com/errata/RHSA-2026:26566
- https://access.redhat.com/errata/RHSA-2026:26590
- https://access.redhat.com/errata/RHSA-2026:26610
- https://access.redhat.com/errata/RHSA-2026:26709
- https://access.redhat.com/errata/RHSA-2026:28923
- https://access.redhat.com/errata/RHSA-2026:29844
- https://access.redhat.com/errata/RHSA-2026:36083
- https://access.redhat.com/errata/RHSA-2026:36085
- https://access.redhat.com/errata/RHSA-2026:36086
- https://access.redhat.com/errata/RHSA-2026:36087
- https://access.redhat.com/errata/RHSA-2026:36632
- https://access.redhat.com/errata/RHSA-2026:36633
- https://access.redhat.com/errata/RHSA-2026:36634
- https://access.redhat.com/errata/RHSA-2026:36768
- https://access.redhat.com/errata/RHSA-2026:36791
- https://access.redhat.com/errata/RHSA-2026:36792
- https://access.redhat.com/errata/RHSA-2026:36798
- https://access.redhat.com/errata/RHSA-2026:38502
- https://access.redhat.com/errata/RHSA-2026:38810
- https://access.redhat.com/errata/RHSA-2026:46377
- https://access.redhat.com/errata/RHSA-2026:46382
- https://access.redhat.com/errata/RHSA-2026:46385
- https://access.redhat.com/errata/RHSA-2026:46392
- https://access.redhat.com/errata/RHSA-2026:46456
- https://access.redhat.com/errata/RHSA-2026:46460
- https://access.redhat.com/errata/RHSA-2026:46473
- https://access.redhat.com/errata/RHSA-2026:49519
- https://access.redhat.com/security/cve/CVE-2026-50257(Third Party Advisory)
- https://bugzilla.redhat.com/show_bug.cgi?id=2485382(Issue Tracking, Third Party Advisory)
- https://gitlab.freedesktop.org/xorg/xserver/-/commit/f5abfb61994471023d8c6470428c8e30c411cc0b(Patch)
- https://lists.x.org/archives/xorg-announce/2026-June/003702.html(Mailing List, Third Party Advisory)
- https://redhat.atlassian.net/browse/PSIRTSUPT-16950(Permissions Required)
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-50257.json
Last updated September 17, 2026 · Source: NVD, CISA KEV, FIRST.org EPSS
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