Vulnerability Description
A heap out-of-bounds write exists in the Photo CD (PCD) decoder of GraphicsMagick. In DecodeImage() (coders/pcd.c), the Huffman delta loop advances its output pointer with q++ after every decoded delta and never checks it against the end of the heap-allocated luma/chroma plane buffers. The pointer is repositioned only when a sync marker introduces a new plane/row; between sync markers the run length is bounded solely by the input. A crafted PCD file that positions the pointer near the end of a plane and then supplies a long run of deltas with no intervening sync therefore walks the pointer past the end of the allocation and writes through it. Processing an untrusted PCD file — for example with gm convert or gm identify, or through any application linked against libGraphicsMagick — can corrupt heap memory beyond the buffers.
Related Weaknesses (CWE)
References
- https://foss.heptapod.net/graphicsmagick/graphicsmagick/-/commit/937cdd9920bd96
- https://foss.heptapod.net/graphicsmagick/graphicsmagick/-/raw/GraphicsMagick-1_3
FAQ
What is CVE-2026-77118?
CVE-2026-77118 is a documented vulnerability. A heap out-of-bounds write exists in the Photo CD (PCD) decoder of GraphicsMagick. In DecodeImage() (coders/pcd.c), the Huffman delta loop advances its output pointer with q++ after every decoded delt...
How severe is CVE-2026-77118?
CVSS scoring is not yet available for CVE-2026-77118. Check NVD for updates.
Is there a patch for CVE-2026-77118?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.