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CVE-2026-50258 is a stack-based buffer overflow in the X Keyboard Extension (XKB) implementation of the X.Org X server and Xwayland. In CheckKeyTypes(), non-canonical key types are validated only for a minimum width and are not rejected when their shift-level count exceeds XkbMaxShiftLevel. Attacker-controlled key types can therefore be accepted and retained with excessive level counts. A subsequent keyboard-mapping update reaches code that derives stack-buffer indices from the unchecked value, overflowing multiple fixed-size stack buffers. The flaw is an incomplete fix for CVE-2025-26597. Affected releases include X.Org X server versions before 21.1.23 and Xwayland versions before 24.1.12.
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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.
27 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 stack buffer overflow in the same advisory batch, mentioned only in passing.
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.