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CVE-2026-50256

high

A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland.

Vendor / product: X.org — x server

A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland. A mismatch between the X server and the libXfont2 library's maximum font name length can cause a stack buffer overflow during font alias resolution. The server allocates a 256 byte stack buffer but libXfont2's alias target name length is 1024 bytes. A font alias name between 257 and 1023 bytes causes the X server to copy that name into the undersized stack buffer without further checks. This may be used to crash the server, or for privilege escalation if the X server runs as root.

CVSS
7.8
7.8 (CVSS v3.1)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Severity source: NVD CVSS v3.1 (secalert@redhat.com)
Timeline (UTC)
Published: 2026-06-05 12:16
Modified: 2026-11-04 23:17
NVD status: Modified
Last synced 1 hour ago
Verified against the source API 2026-11-04 23:38 UTC
Exploitation
Not listed in CISA KEV (as of last catalog sync)
Absence from KEV does not mean a CVE is not exploited. Exploitation status: unknown (no authoritative evidence in our sources).

Affected products

x.org / x_server <21.1.23
x.org / xwayland <24.1.12
redhat / enterprise_linux 7.0, 8.0, 9.0, 10.0

Weakness classification (CWE)

CWE-121

Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.

Mitigation & advisories

Vendor advisory: https://access.redhat.com/security/cve/CVE-2026-50256
Vendor advisory: https://bugzilla.redhat.com/show_bug.cgi?id=2485380
Vendor advisory: https://access.redhat.com/security/cve/CVE-2026-50256
Vendor advisory: https://bugzilla.redhat.com/show_bug.cgi?id=2485380
Patch / mitigation: https://gitlab.freedesktop.org/xorg/xserver/-/commit/bb5158f962dc935e58ef8b4b5fcb31be201a6e07

References

Data sources

NVD CVE API 2.0 — fetched 2026-11-04 23:38 UTC · record ↗

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Understanding CVEs and CVSS Scores

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