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CVE-2026-50257 is a use-after-free vulnerability in the XSYNC extension of the X.Org X server and Xwayland, in miSyncDestroyFence(). Unsafe traversal of a fence trigger list permits callbacks invoked during destruction to free trigger-list entries and associated await state that subsequent loop processing still references. An attacker can arrange multiple triggers on a fence and use a second X client connection to destroy that fence, causing a dereference of freed memory, including a potentially freed function pointer.
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What an attacker gets, and what they’ve been doing with it.
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Patch, then assume compromise.
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
25 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A vulnerability addressed by the Huawei EulerOS_SA-2026-3320 security advisory; no technical flaw details are provided.
A vulnerability addressed by the EulerOS_SA-2026-3395 advisory; no technical flaw details are provided.
A vulnerability fixed in X.Org Server 21.1.23 and xwayland 24.1.12, also noted as addressed in the discussed XLibre release.
A use-after-free vulnerability in the X.Org X server/Xwayland XSYNC extension, specifically in miSyncDestroyFence(), that can cause denial of service or local privilege escalation, including full system compromise when the X server runs as root.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.