# CVE-2026-121604: wlroots before 0.20.2 Out-of-Bounds Read via read_surface_class() in xwm.c

Status: published. Published: 2026-11-03. Updated: 2026-11-03.

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.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://gitlab.freedesktop.org/wlroots/wlroots/-/commit/851cdd0089004884bd85a95ad21f04009cb5a53a
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://gitlab.freedesktop.org/wlroots/wlroots/-/commit/4412992469540b1d578cb94a5cd4e6e5829812dc

## Affected products and versions

- wlroots / wlroots: ≥ 0; < 0.20.2 (affected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 4.8 (medium); CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 3.3 (low); CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N; source: CNA: VulnCheck

- CVSS 4.0: 4.8 (medium); CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X; source: NVD: disclosure@vulncheck.com

- CVSS 3.1: 3.3 (low); CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-125

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://gitlab.freedesktop.org/wlroots/wlroots/-/work_items/4092 (CNA: VulnCheck; issue-tracking)

- https://gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/5374 (CNA: VulnCheck; issue-tracking)

- https://gitlab.freedesktop.org/wlroots/wlroots/-/commit/851cdd0089004884bd85a95ad21f04009cb5a53a (CNA: VulnCheck; patch)

- https://gitlab.freedesktop.org/wlroots/wlroots/-/commit/4412992469540b1d578cb94a5cd4e6e5829812dc (CNA: VulnCheck; patch)

- https://gitlab.freedesktop.org/wlroots/wlroots/-/releases/0.20.2 (CNA: VulnCheck; release-notes)

- https://gitlab.freedesktop.org/wlroots/wlroots/-/blob/0.20.1/xwayland/xwm.c#L661-L678 (CNA: VulnCheck; technical-description)

- https://www.vulncheck.com/advisories/wlroots-before-0.20.2-out-of-bounds-read-via-read-surface-class-in-xwm-c (CNA: VulnCheck; third-party-advisory)

- https://gitlab.freedesktop.org/wlroots/wlroots/-/blob/0.20.1/xwayland/xwm.c#L661-L678 (disclosure@vulncheck.com)

- https://gitlab.freedesktop.org/wlroots/wlroots/-/commit/4412992469540b1d578cb94a5cd4e6e5829812dc (disclosure@vulncheck.com)

- https://gitlab.freedesktop.org/wlroots/wlroots/-/commit/851cdd0089004884bd85a95ad21f04009cb5a53a (disclosure@vulncheck.com)

- https://gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/5374 (disclosure@vulncheck.com)

- https://gitlab.freedesktop.org/wlroots/wlroots/-/releases/0.20.2 (disclosure@vulncheck.com)

- https://gitlab.freedesktop.org/wlroots/wlroots/-/work_items/4092 (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/wlroots-before-0.20.2-out-of-bounds-read-via-read-surface-class-in-xwm-c (disclosure@vulncheck.com)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-121604; retrieved 2026-11-03; source updated 2026-11-03

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-121604; retrieved 2026-11-03; source updated 2026-11-03

Revision: 342c24bbcdd3f7aca1213637f94dcd0a2365fd07349f7087188c8a442dcab874

Canonical: https://y2.dev/cve/CVE-2026-121604

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