What is CVE-2026-123785?

CVE-2026-123785 is a medium-severity vulnerability in Fluxbox, classified under Loop with Unreachable Exit Condition (Infinite Loop). CVSS score: 5.5/10. Published 2026-11-06.

How severe is CVE-2026-123785?

Medium severity. CVSS v3 base score is 5.5 out of 10.

Vulnerability in Fluxbox

CVE-2026-123785

Fluxbox through 1.3.7 contains an infinite loop vulnerability in Menu::updateMenu() in src/FbTk/Menu.cc that allows attackers to hang the window manager via crafted style geometry values. Attackers can supply a style with an oversized unbounded menu.titleHeight so the column loop never terminates, causing sustained CPU use and denial of service at startup.

Published 2026-11-06 · last modified 2026-11-06.

CVSS v3 metric

CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.

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

Fluxbox

Weakness classification (CWE)

CWE-835 — Loop with Unreachable Exit Condition (Infinite Loop)

References

github.com/fluxbox/fluxbox (product)
Menu::updateMenu column loop (technical-description)
Pull Request #90 (issue-tracking, patch)
VulnCheck Advisory: Fluxbox through 1.3.7 Infinite Loop via Menu::updateMenu() Style Geometry (third-party-advisory)

Frequently asked questions

What is CVE-2026-123785?: CVE-2026-123785 is a medium-severity vulnerability in Fluxbox, classified under Loop with Unreachable Exit Condition (Infinite Loop). CVSS score: 5.5/10. Published 2026-11-06.
How severe is CVE-2026-123785?: Medium severity. CVSS v3 base score is 5.5 out of 10.