PatchSiren cyber security CVE debrief
CVE-2026-34001 Red Hat CVE debrief
A use-after-free vulnerability in the X.Org X server's XSYNC fence triggering logic, specifically within the miSyncTriggerFence() function, was disclosed on 2026-04-23 and last modified on 2026-05-28. The flaw allows an attacker with access to the X11 server to trigger a server crash and potentially achieve memory corruption without requiring user interaction. The vulnerability is rated HIGH severity with a CVSS score of 7.8. Multiple Red Hat Security Advisories have been issued addressing this vulnerability across various product versions. The weakness is classified as CWE-825 (Expired Pointer Dereference).
- Vendor
- Red Hat
- Product
- Red Hat Enterprise Linux 10
- CVSS
- HIGH 7.8
- CISA KEV
- Not listed in stored evidence
- Original CVE published
- 2026-04-23
- Original CVE updated
- 2026-05-28
- Advisory published
- 2026-04-23
- Advisory updated
- 2026-05-28
Who should care
System administrators managing Linux workstations and servers with X11 environments, security teams responsible for graphical desktop infrastructure, and organizations running Red Hat Enterprise Linux or derivative distributions with X.Org server deployments.
Technical summary
The vulnerability exists in the XSYNC fence triggering logic within the X.Org X server's miSyncTriggerFence() function. A use-after-free condition can be triggered by an attacker with local access to the X11 server, leading to server crashes and potential memory corruption. The attack requires no user interaction and has low complexity. The CVSS 3.1 vector (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) indicates that while the attack is local, successful exploitation yields high impact across confidentiality, integrity, and availability dimensions. The underlying weakness is CWE-825 (Expired Pointer Dereference).
Defensive priority
HIGH
Recommended defensive actions
- Apply relevant Red Hat Security Advisory patches as indicated by RHSA-2026:10739, RHSA-2026:11352, RHSA-2026:11369, RHSA-2026:11388, RHSA-2026:11656, RHSA-2026:11692, RHSA-2026:13414, and subsequent advisories
- Restrict local access to the X11 server to trusted users only
- Monitor for unexpected X server crashes as potential exploitation indicators
- Review X.Org server version and upgrade to patched releases when available
- Consider disabling unnecessary XSYNC extension usage if not required for operations
Evidence notes
Vulnerability description sourced from NVD record. CVSS vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H indicates local attack vector with low attack complexity, low privileges required, no user interaction, and high impact on confidentiality, integrity, and availability. Weakness classification CWE-825 from Red Hat source. Multiple RHSA errata issued between 2026-04-23 and 2026-05-28 indicate active vendor response.
Official resources
2026-04-23