CVE-2026-55999

A flaw was found in the glamor_font_get() function of the xorg-x11-server. This vulnerability, a heap buffer overflow, occurs when the server processes a specially crafted PCF font file where individual glyph metrics exceed the declared maximum bounds. An authenticated X client can exploit this by loading a malicious font and drawing text, potentially leading to arbitrary code execution with attacker-controlled content and extent. This affects servers utilizing the glamor acceleration backend, such as Xorg with the modesetting driver and Xwayland.

This Important flaw in xorg-x11-server allows an authenticated X client to achieve arbitrary code execution. By processing a malicious PCF font file where glyph metrics exceed declared bounds, a heap buffer overflow occurs within the glamor acceleration backend. This vulnerability primarily impacts Red Hat systems running Xorg with the modesetting driver or Xwayland, typically found in desktop environments.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.