Local Heap Overflow via PCX Font in Xorg-Server <21.2.24 (SetFont)
CVE-2026-55999 Published on July 8, 2026
xorg-server / xwayland glamor font atlas Heap Buffer Overflow
Local attackers with a X connection able to provide PCX fonts to the X
server xorg-server before 21.2.24 and xwayland before 24.1.13 could
cause a heap buffer overflow via SetFont due to missing glyph boundary checks.
Vulnerability Analysis
CVE-2026-55999 can be exploited with network access, and requires small amount of user privileges. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to be very high.
Weakness Type
Heap-based Buffer Overflow
A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().
Products Associated with CVE-2026-55999
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Affected Versions
X.Org xorg-server:- Before 21.1.24 is affected.
- Before 24.1.13 is affected.