FLTK: Stack-based buffer overflow in BMP image loader
Summary
FLTK through version 1.4.5 contains a stack-based buffer overflow in the BMP image loader (Fl_BMP_Image::load_bmp_()). A crafted BMP or ICO file with a colors_used value above 256 overflows the 768-byte colormap array on the stack. An attacker can cause a crash or possibly execute code if a user opens such a file in an FLTK-based application, and exploitation requires user interaction.
Affected
- FLTK 0 to 1.4.5
- Applications built with affected FLTK versions that load BMP or ICO files
- Linux distribution FLTK packages (fix status unknown)
Fixed in
- Unknown from vendor sources. VulDB recommends FLTK 1.4.6 or later; this version has not been independently verified.
Workaround
- No official workaround.
- Until a patched version is installed, do not open BMP or ICO files from untrusted sources in FLTK-based applications.
Exploitation
- Not listed in CISA KEV; not known to be exploited.
- VulDB reports no public exploit. A third-party write-up is referenced, but its content has not been verified.
- EPSS: 0.0016.
Our recommendation
- Inventory applications that use FLTK, including vendor software.
- Ask vendors for builds based on FLTK 1.4.6 or later and install them.
- Check the Red Hat, SUSE, Debian and Ubuntu advisories for distribution fixes.
- Avoid opening untrusted image files in affected tools.
- Priority: low to medium for a typical SME without FLTK-based software that processes external files.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- VulDB CVE-2026-116723 vuldb.com
- VulDB vulnerability 426967 vuldb.com
- VulnCheck advisory www.vulncheck.com
- FLTK GitHub commit 3a049d8 github.com
- FLTK GitHub issue 1632 github.com
- FLTK Fl_BMP_Image.cxx at release-1.4.5 github.com
- OpenCVE CVE-2026-116723 app.opencve.io
- SUSE CVE entry CVE-2026-116723 vulners.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 1 Nov 2026, 10:04.
Original description (NVD)
FLTK through 1.4.5 contains a stack-based buffer overflow vulnerability in Fl_BMP_Image::load_bmp_() that allows attackers to corrupt stack memory by supplying an oversized BMP colors_used field. Attackers can craft BMP or ICO files with colors_used above 256 to overflow the 768-byte colormap array, causing crashes or potential code execution.
NVD references (6)
- https://github.com/fltk/fltk
- https://github.com/fltk/fltk/blob/release-1.4.5/src/Fl_BMP_Image.cxx#L255-L265
- https://github.com/fltk/fltk/commit/3a049d8262dc759cf9737339420e8457e24c0cb1
- https://github.com/fltk/fltk/issues/1632
- https://hackmd.io/@haindpwn/fltk-bmp-image-stack-heap-overflow
- https://www.vulncheck.com/advisories/fltk-through-1.4.5-stack-buffer-overflow-via-fl-bmp-image-colors-used-fi…
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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