# 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.

- **Severity:** High 8.4 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **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:** Yes
- **Published:** 20 Aug 2026
- **Updated:** 26 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-77118, ECHO-a2fc-1e4e-dfa3, GHSA-qjrj-qxx7-fc4j, OESA-2026-3656, UBUNTU-CVE-2026-77118

## 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 (Out-of-bounds Write)

## Which versions are affected by CVE-2026-77118?


## How do I fix CVE-2026-77118?

Apply the vendor's patch.

## Is CVE-2026-77118 being exploited?

There is no known exploitation of CVE-2026-77118 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-77118 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-77118 in the wild and no public exploit code.

Affected product: Debian GraphicsMagick. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-77118/ (Markdown: https://insights.sbomify.com/CVE-2026-77118/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-77118
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-77118
- OSV: https://osv.dev/vulnerability/CVE-2026-77118

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-77118/
Summaries are generated and may contain mistakes; the official description above is the record.