# CVE-2026-47178: Strukturag libheif heap out-of-bounds write in uncompressed tile decoder

Source: https://junglewise.ai/threats/cve-2026-47178-strukturag-libheif-heap-out-of-bounds-write-in-uncompressed-tile  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-21. Updated: 2026-07-21  
License: CC BY 4.0 with a link back

CVE-2026-47178 · Severity: medium · CVSS 6.1 · Published 2026-07-21

libheif is a widely used software library for processing HEIF and AVIF image files, commonly found in image viewers, web servers, and photo editing tools. A security flaw allows a specially crafted image file to cause a memory error when opened, potentially leading to a program crash or allowing an attacker to take control of the application. This could impact services that automatically process user-uploaded images, such as social media platforms or cloud storage providers.

## Quick answers

**Is CVE-2026-47178 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-47178 being exploited in the wild.

**How severe is CVE-2026-47178?** Medium severity, with a CVSS score of 6.1, published 21 July 2026.

**Which products and versions are affected?** strukturag libheif 1.19.0 - 1.21.2.

**Is there a fix for CVE-2026-47178?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-47178 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-47178?** Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A heap out-of-bounds write exists in libheif's uncompressed 'unci' codec subsystem, specifically within the unc_decoder_component_interleave::decode_tile() function. The vulnerability is caused by an incorrect row offset calculation where full-resolution tile origins are used against halved chroma plane strides in 4:2:0 interleaved images. An attacker can exploit this by providing a crafted HEIF file that overwrites the C++ vtable pointer of an adjacent object. This allows for a controlled indirect call, potentially leading to arbitrary code execution when the next virtual function is dispatched. The issue is fixed in version 1.22.0.

## Affected products

- strukturag libheif 1.19.0 - 1.21.2

## Timeline

- 2026-05-19: disclosed: Initial disclosure on GitHub
- 2026-07-21: advisory: NVD publication date

## References

- [https://github.com/strukturag/libheif/security/advisories/GHSA-5x55-x5pf-9c6g](https://github.com/strukturag/libheif/security/advisories/GHSA-5x55-x5pf-9c6g)