---
id: "CVE-2026-116724"
kind: "vulnerability"
aliases: ["CVE-2026-116724"]
title: "FLTK: crafted BMP or ICO file overflows heap buffer during image load"
severity: "high"
cvss: 8.5
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["c++", "desktop-apps", "fltk", "image-parsing", "package"]
not_affected_if: ["trusted-assets-only"]
published_at: "2026-10-26T22:16:56+00:00"
first_seen_at: "2026-10-26T22:25:33+00:00"
updated_at: "2026-10-26T22:27:36+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-116724", "first_seen_at": "2026-10-26T22:25:33+00:00"}]
---

# FLTK: crafted BMP or ICO file overflows heap buffer during image load

FLTK, a C++ GUI toolkit, miscalculates the pixel buffer size for BMP images from file-supplied width and height due to an integer overflow in Fl_BMP_Image::load_bmp_(). A crafted BMP or ICO file makes the decoder write past the heap buffer, which can corrupt application memory.

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

## How to check

- Check the FLTK version in use: `fltk-config --version` or the version in the project's dependency lockfile, and see whether it is `1.4.5` or earlier.
- Find code that loads images with Fl_BMP_Image or Fl_Shared_Image from untrusted or user-supplied files.

## Fix

- Upgrade FLTK to a release newer than `1.4.5` once a patched version is published (unknown from the sources).
- Until patched, reject or do not load BMP and ICO files from untrusted sources.

## Timeline

- 2026-10-26T22:25:33+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-116724

## From the sources

FLTK through 1.4.5 contains an integer overflow vulnerability in Fl_BMP_Image::load_bmp_() that causes undersized pixel buffer allocation from file-supplied width and height. Attackers can supply a crafted BMP or ICO file with large dimensions so row decoding writes file-derived data past the heap buffer, corrupting the application heap.

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