CVE-2025-26601: tigervnc Use-After-Free (CVSS 7.8)

Description

A use-after-free flaw was found in X.Org and Xwayland. When changing an alarm, the values of the change mask are evaluated one after the other, changing the trigger values as requested, and eventually, SyncInitTrigger() is called. If one of the changes triggers an error, the function will return early, not adding the new sync object, possibly causing a use-after-free when the alarm eventually triggers.

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CVSS v3.1 Score

7.8

HIGH

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Weakness Type (CWE)

CWE-416 Use After Free

Affected Products

Vendor	Product	Versions
tigervnc	tigervnc	All
x.org	x_server	< 21.1.16
x.org	xwayland	< 24.1.6
redhat	enterprise_linux	All
redhat	enterprise_linux	All
redhat	enterprise_linux	All

References

Other References

https://access.redhat.com/errata/RHSA-2025:2500 https://access.redhat.com/errata/RHSA-2025:2502 https://access.redhat.com/errata/RHSA-2025:2861 https://access.redhat.com/errata/RHSA-2025:2862 https://access.redhat.com/errata/RHSA-2025:2865 https://access.redhat.com/errata/RHSA-2025:2866 https://access.redhat.com/errata/RHSA-2025:2873 https://access.redhat.com/errata/RHSA-2025:2874 https://access.redhat.com/errata/RHSA-2025:2875 https://access.redhat.com/errata/RHSA-2025:2879

Frequently Asked Questions

What is CVE-2025-26601? +

A use-after-free flaw was found in X.Org and Xwayland. When changing an alarm, the values of the change mask are evaluated one after the other, changing the trigger values as requested, and eventually, SyncInitTrigger() is called. If one of the changes triggers an error, the function will return early, not adding the new sync object, possibly causing a use-after-free when the alarm eventually triggers. It has a CVSS v3.1 base score of 7.8 (HIGH).

How severe is CVE-2025-26601? +

CVE-2025-26601 has a CVSS v3.1 score of 7.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2025-26601? +

CVE-2025-26601 affects products from redhat, tigervnc, x.org, specifically: enterprise_linux, tigervnc, x_server, xwayland. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-26601? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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