What is CVE-2026-123784?

CVE-2026-123784 is a high-severity vulnerability in Fluxbox, classified under OS Command Injection. CVSS score: 7.8/10. Published 2026-11-06.

How severe is CVE-2026-123784?

High severity. CVSS v3 base score is 7.8 out of 10.

RCE in Fluxbox

CVE-2026-123784

Fluxbox through 1.3.7 contains an OS command injection vulnerability in RootTheme::reconfigTheme() that allows attackers to execute commands via crafted style background values. Attackers can embed shell metacharacters in background pixmap paths, random directories, or gradient texture text, which are concatenated unescaped into an fbsetbg command run via $SHELL -c when the style loads.

Vulnerability class: Command Injection (OS Command Injection)

Published 2026-11-06.

CVSS v3 metric

CVSS v3 base score 7.8 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/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-78 — OS Command Injection

References

github.com/fluxbox/fluxbox (product)
RootTheme::reconfigTheme (technical-description)
Fix commit 270bfbc (patch)
Pull Request #89 (issue-tracking, patch)
VulnCheck Advisory: Fluxbox through 1.3.7 OS Command Injection via Style Background Values (third-party-advisory)

Frequently asked questions

What is CVE-2026-123784?: CVE-2026-123784 is a high-severity vulnerability in Fluxbox, classified under OS Command Injection. CVSS score: 7.8/10. Published 2026-11-06.
How severe is CVE-2026-123784?: High severity. CVSS v3 base score is 7.8 out of 10.