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CVE-2026-50259 is a stack-based buffer overflow in the XKB extension of the X.Org X server and Xwayland. The vulnerable _XkbSetMapChecks() routine allocates a 256-element stack buffer, mapWidths, while CheckKeyTypes() derives the number of entries to write from client-controlled XKB SetMap request fields. An incomplete boundary validation permits a key-type index at the current type-count boundary and fails to ensure that the computed map count fits the buffer. A connected X client can cause writes beyond mapWidths, corrupting the adjacent stack variable. The issue is an incomplete fix for CVE-2025-26597.
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No public exploit code observed for this vulnerability.
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Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
23 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-based buffer overflow in the X.Org X server XKB extension caused by an incomplete bounds check in CheckKeyTypes(), allowing a connected X client to crash the server and potentially achieve local privilege escalation 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.