Stack-based buffer overflow in X.Org X server and Xwayland CheckKeyTypes()
CVE-2026-50258 is a stack-based buffer overflow vulnerability in the X.Org X server and Xwayland. The flaw is in XKB key type handling: multiple stack buffers are sized for XkbMaxShiftLevel * XkbNumKbdGroups, but CheckKeyTypes() does not verify or clamp non-canonical key types to XkbMaxShiftLevel. As a result, a malicious client can supply key types with excessive shift levels, causing writes past the bounds of stack-allocated buffers and triggering stack overflows. The issue is described as an incomplete fix for CVE-2025-26597. Affected versions are X.Org X server prior to 21.1.23 and Xwayland prior to 24.1.12.
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Impact
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Mitigation
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Remediation
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Exploits
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No public exploit code observed for this vulnerability.
Affected products & vendors
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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.
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Every observed campaign linking this CVE to a named adversary.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.