---
id: "CVE-2026-123785"
page: "https://infrastack.ai/live/CVE-2026-123785"
kind: "vulnerability"
aliases: ["CVE-2026-123785"]
title: "Fluxbox: crafted style values hang the window manager in an endless loop"
severity: "medium"
cvss: 6.8
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["fluxbox", "linux-desktop", "package", "window-manager"]
not_affected_if: ["default-style-only", "other-window-manager"]
published_at: "2026-11-06T15:17:21+00:00"
first_seen_at: "2026-11-06T15:42:44+00:00"
updated_at: "2026-11-06T15:44:27+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-123785", "first_seen_at": "2026-11-06T15:42:44+00:00"}]
exploit_sources: []
---

# Fluxbox: crafted style values hang the window manager in an endless loop

Link for people: https://infrastack.ai/live/CVE-2026-123785 (this .md is for agents)

Fluxbox, a Linux window manager, loops forever in its menu update code when a style file sets an oversized menu title height. An attacker who gets a crafted style loaded can hang the window manager and cause a denial of service at startup.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Run `fluxbox -version` or check the installed package version to see whether it is `1.3.7` or earlier
- Look for a custom style file that sets `menu.titleHeight` to an unusually large value

## Timeline

- 2026-11-06T15:42:44+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-123785

## Documents

- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/fluxbox-through-1.3.7-infinite-loop-via-menu-updatemenu-style-geometry

## From the sources

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.

---

_Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai_