CVE-2026-50257: Use After Free in Red Hat Red Hat Enterprise Linux 10
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.
AI Analysis
Technical Summary
This vulnerability involves a use-after-free condition in the miSyncDestroyFence() function of the X.Org X server and Xwayland. An attacker with local access can connect to the X server, set up multiple fence triggers, and cause a use-after-free function pointer call by destroying a fence from a second X connection. This can result in a denial of service (server crash) or privilege escalation when the X server operates with root privileges. Red Hat has issued security advisories RHSA-2026:26562 and RHSA-2026:26566 providing patches for affected versions of Red Hat Enterprise Linux 8 and 10, respectively, fixing this and other related vulnerabilities.
Potential Impact
Successful exploitation of this use-after-free vulnerability can cause the X server to crash, resulting in denial of service. Additionally, if the X server runs as root, the flaw may be leveraged for privilege escalation, potentially allowing an attacker to execute code with elevated privileges. The CVSS v3.1 base score is 7.8, indicating high severity with high impact on confidentiality, integrity, and availability.
Mitigation Recommendations
Red Hat has released official security updates that fix this vulnerability in the xorg-x11-server and xorg-x11-server-Xwayland packages. Users should apply the updates provided in Red Hat Enterprise Linux 8 versions prior to 8.10.2 and Red Hat Enterprise Linux 10 versions prior to 10.2.2. Refer to Red Hat advisories RHSA-2026:26562 and RHSA-2026:26566 and the update instructions at https://access.redhat.com/articles/11258 for detailed remediation steps. Applying these updates fully mitigates the vulnerability.
CVE-2026-50257: Use After Free in Red Hat Red Hat Enterprise Linux 10
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.
CVSS v3.1
Score 7.8high
Affected software
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability involves a use-after-free condition in the miSyncDestroyFence() function of the X.Org X server and Xwayland. An attacker with local access can connect to the X server, set up multiple fence triggers, and cause a use-after-free function pointer call by destroying a fence from a second X connection. This can result in a denial of service (server crash) or privilege escalation when the X server operates with root privileges. Red Hat has issued security advisories RHSA-2026:26562 and RHSA-2026:26566 providing patches for affected versions of Red Hat Enterprise Linux 8 and 10, respectively, fixing this and other related vulnerabilities.
Potential Impact
Successful exploitation of this use-after-free vulnerability can cause the X server to crash, resulting in denial of service. Additionally, if the X server runs as root, the flaw may be leveraged for privilege escalation, potentially allowing an attacker to execute code with elevated privileges. The CVSS v3.1 base score is 7.8, indicating high severity with high impact on confidentiality, integrity, and availability.
Mitigation Recommendations
Red Hat has released official security updates that fix this vulnerability in the xorg-x11-server and xorg-x11-server-Xwayland packages. Users should apply the updates provided in Red Hat Enterprise Linux 8 versions prior to 8.10.2 and Red Hat Enterprise Linux 10 versions prior to 10.2.2. Refer to Red Hat advisories RHSA-2026:26562 and RHSA-2026:26566 and the update instructions at https://access.redhat.com/articles/11258 for detailed remediation steps. Applying these updates fully mitigates the vulnerability.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- redhat
- Date Reserved
- 2026-06-04T14:55:24.011Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
- Vendor Advisory Urls
- [{"url":"https://access.redhat.com/security/cve/CVE-2026-50257","vendor":"Red Hat"}]
Threat ID: 6a22b798e29bf47b506379e4
Added to database: 06/05/2026, 11:48:40 UTC
Last enriched: 07/30/2026, 01:42:00 UTC
Last updated: 07/31/2026, 21:26:48 UTC
Views: 59
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