A critical security vulnerability has been discovered in X.Org and Xwayland, which could potentially lead to arbitrary code execution, denial of service, or sensitive data exposure in affected systems. CVE-2025-26601 refers to a use-after-free vulnerability, which was found in the way alarm changes were being handled in X.Org and Xwayland. This article aims to provide a detailed overview of the said vulnerability, explaining its likely cause, impact, and what users can do to protect their systems.
Vulnerability Details
The issue exists in the part of the code that deals with changing an alarm and evaluating the values of the change mask one after the other. When SyncInitTrigger() is called, it sets the new trigger values as requested. However, if any of the changes result in an error, the function returns early, without creating a proper sync object. This leads to a use-after-free situation when the alarm eventually triggers, potentially causing arbitrary code execution or denial of service on the system. The exploit is explained in terms of code snippets below.
Code Snippet
´´´c
SyncChangeAlarm
...
mask, pParms))
{
if (status != BadValue) {
/* there were no changes causing an error */
SECURITY_VERIFY_GEOMETR(pWin, stuff->drawable, SecurityWriteAccess);
/* early return from function */
return;
}
}
SyncInstallAlarm(pWin, pNewAlarm);
...
´´´
Original References
The vulnerability was originally reported by a security researcher and later discussed in detail by different security forums. Some noteworthy links discussing the vulnerability are:
* Original Advisory
* Mitigation guide
* Bugzilla report
Exploit Details
The use-after-free issue makes it possible for attackers to craft a specific series of changes to the alarm system, triggering an error, and not creating a sync object. Once the alarm activates, the system tries to use the corrupted memory, potentially leading to arbitrary code execution, denial of service, or data leakage. While there are no known exploits in the wild, it is highly recommended to update immediately to prevent potential attacks.
Mitigation
As the vulnerability affects both X.Org and Xwayland, users are advised to apply patches provided by their respective upstream vendors as soon as possible. Additionally, users should follow best practices for system hardening, including proper access controls and network security measures.
Conclusion
This use-after-free vulnerability (CVE-2025-26601) in X.Org and Xwayland highlights the importance of staying updated with the latest security patches and keeping abreast of the evolving threat landscape. Regularly applying updates and adopting good security practices are essential in safeguarding our systems from potential exploits.
Timeline
Published on: 02/25/2025 16:15:39 UTC