CVE-2026-34001
Published: 23 April 2026
Summary
CVE-2026-34001 is a high-severity Expired Pointer Dereference (CWE-825) vulnerability. Its CVSS base score is 7.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 0.3th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-16 (Memory Protection) and SI-2 (Flaw Remediation).
Deeper analysis
CVE-2026-34001, published on 2026-04-23, is a use-after-free vulnerability (CWE-825) in the X.Org X server. The flaw resides in the XSYNC fence triggering logic, specifically within the miSyncTriggerFence() function, affecting the X11 server component.
Local attackers with low privileges can exploit this issue without user interaction, as indicated by the CVSS v3.1 vector AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H (base score 7.8). Successful exploitation triggers a server crash and enables memory corruption, potentially resulting in denial of service or further system compromise.
Red Hat has released multiple errata addressing this vulnerability, including RHSA-2026:10739, RHSA-2026:11352, RHSA-2026:11369, RHSA-2026:11388, and RHSA-2026:11656, which provide patched packages for affected systems.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-25230
Vulnerability details
A flaw was found in the X.Org X server. This use-after-free vulnerability occurs in the XSYNC fence triggering logic, specifically within the miSyncTriggerFence() function. An attacker with access to the X11 server can exploit this without user interaction, leading to…
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a server crash and potentially enabling memory corruption. This could result in a denial of service or further compromise of the system.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Use-after-free in X server enables local memory corruption for privilege escalation (T1068) and server crash for DoS via application exploitation (T1499.004).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Timely flaw remediation via vendor patches like Red Hat errata directly fixes the use-after-free vulnerability in the X.Org X server's miSyncTriggerFence function.
Memory protection mechanisms such as address space layout randomization and guard pages minimize exploitation of use-after-free flaws leading to corruption or crashes.
Least privilege enforcement on the X server restricts impact of local low-privilege exploitation attempts causing memory corruption or denial of service.