xorg-x11-server-xwayland security update (CVE-2025-62231)

The X.Org X server and Xwayland implementations contain multiple security flaws. CVE-2025-62231 is an unsigned short overflow in the XkbSetCompatMap() function due to improper bounds checking, potentially causing memory corruption or crashes. Additional vulnerabilities include out-of-bounds reads in XKB modifier map handling (CVE-2026-34002) and key types request validation (CVE-2026-34003), which can lead to sensitive information disclosure or denial of service. Other critical issues fixed in xorg-server 21.1.23 and xwayland 24.1.12 include a font alias stack-based buffer overflow, use-after-free in miSyncDestroyFence(), and multiple stack-based buffer overflows in XKB key types and set map requests. These vulnerabilities were discovered by anonymous researchers working with TrendAI Zero Day Initiative and assigned CVEs 2026-50256 through 2026-50259. The fixes address buffer size mismatches, improper validation, and use-after-free conditions.

Successful exploitation of these vulnerabilities can lead to memory corruption, server crashes causing denial of service, and potential exposure of sensitive information. The vulnerabilities are remotely exploitable without privileges or user interaction, making them critical. The impact includes confidentiality loss and availability disruption of the X.Org X server and Xwayland services.

Official security fixes are available in xorg-server version 21.1.23 and xwayland version 24.1.12. Users and administrators should upgrade to these versions to remediate the vulnerabilities. No additional mitigation steps are indicated by the vendor advisory.