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CVE-2026-55999 is a heap-based buffer overflow in the Glamor 2D-acceleration font atlas path of X.Org X server and Xwayland. In glamor_font_get(), atlas slot dimensions are derived from a font's declared maxbounds, while glyph bitmap copies use individual glyph metrics without verifying that those metrics are non-negative and fit within the allocated slot. A crafted PCF font can declare small maxbounds while supplying oversized per-glyph metrics, causing writes beyond the heap-allocated atlas buffer. Negative metrics can additionally induce unsigned integer wrapping in loop bounds or copy sizes. The issue affects Glamor-backed servers, including Xorg using the modesetting driver and Xwayland, before xorg-server 21.1.24 and xwayland 24.1.13.
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No public exploit code observed for this vulnerability.
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27 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A vulnerability in the Xorg X server that may permit privilege escalation when the X server runs with privileges.
A high-impact local vulnerability affecting Huawei EulerOS 2.0 Xorg X11 server packages, with low attack complexity, low privileges required, and high confidentiality, integrity, and availability impact.
A high-impact local vulnerability requiring low privileges and no user interaction, with high confidentiality, integrity, and availability impact according to the supplied CVSS vector. It is addressed by EulerOS_SA-2026-3395.
A vulnerability tracked as CVE-2026-55999 affecting X.Org X11 server packages on Oracle Linux 7. The supplied CVSS v3 vector indicates a local, low-complexity attack requiring low privileges, with high confidentiality, integrity, and availability impact.
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.