Use-after-free in X.Org X server and Xwayland FreeCounter()
CVE-2026-50260 is a use-after-free vulnerability in the XSYNC component of the X.Org X server and Xwayland, specifically in FreeCounter(). A malicious client can set up multiple SyncCounters and wait on triggers associated with those counters, then use a second client connection to destroy the counters while they are still referenced. This results in stale references being used after the underlying counter objects have been freed. The issue affects X.Org X server versions prior to 21.1.23 and Xwayland versions prior to 24.1.12.
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Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
If you can’t patch tonight, do this now.
Remediation
Patch, then assume compromise.
Exploits
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Affected products & vendors
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.
Recent activity
6 sources tracked across advisories and community write-ups. News coverage will land here when it surfaces.
No news coverage yet. Advisories and community discussion only.
The version that knows your environment.
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.