CVE-2026-77118 Out-of-bounds write in GraphicsMagick PCD decoder
A heap out-of-bounds write in the GraphicsMagick PCD decoder allows attackers to corrupt memory and potentially execute code by processing a crafted image file.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-77118?
CVE-2026-77118 is a high-severity memory corruption vulnerability in Debian GraphicsMagick, published on 20 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-787
Which versions are affected by CVE-2026-77118?
How do I fix CVE-2026-77118?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-77118 being exploited?
There is no known exploitation of CVE-2026-77118 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-77118, ECHO-a2fc-1e4e-dfa3, GHSA-qjrj-qxx7-fc4j, OESA-2026-3656, UBUNTU-CVE-2026-77118.