Out-of-bounds Read in Wlroots
CVE-2026-121604
wlroots before 0.20.2 contains an out-of-bounds read vulnerability in read_surface_class() in xwayland/xwm.c that allows local X11 clients to leak compositor heap memory. Attackers can set a WM_CLASS property with a NUL-terminated instance but unterminated class, exposing over-read heap bytes as the window class or app_id over IPC.
Vulnerability class: Buffer Overflow
Published .
CVSS v3 metric
CVSS v3 base score 3.3 (Low). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- gitlab.freedesktop.org/wlroots/wlroots/-/work_items/4092 (issue-tracking)
- gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/5374 (issue-tracking)
- gitlab.freedesktop.org/wlroots/wlroots/-/commit/851cdd0089004884bd85a95ad21f040… (patch)
- gitlab.freedesktop.org/wlroots/wlroots/-/commit/4412992469540b1d578cb94a5cd4e6e… (patch)
- gitlab.freedesktop.org/wlroots/wlroots/-/releases/0.20.2 (release-notes)
- gitlab.freedesktop.org/wlroots/wlroots/-/blob/0.20.1/xwayland/xwm.c (technical-description)
- www.vulncheck.com/advisories/wlroots-before-0.20.2-out-of-bounds-read-via-read-… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-121604?
- CVE-2026-121604 is a low-severity vulnerability in Wlroots, classified under Out-of-bounds Read. CVSS score: 3.3/10. Published 2026-11-03.
- How severe is CVE-2026-121604?
- Low severity. CVSS v3 base score is 3.3 out of 10.