# CVE-2026-84383: libheif heap overflow in scale_nearest_neighbor via duplicate alpha planes

Source: https://junglewise.ai/threats/cve-2026-84383-libheif-is-a-heif-and-avif-file-format-decoder-and-encoder-from-1  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-18. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-84383 · Severity: critical · CVSS 9.8 · Published 2026-09-18

libheif is a decoder and encoder for HEIF, HEIC, and AVIF image formats commonly used in modern devices and applications. A malicious image file can exploit the way libheif handles alpha transparency layers, causing it to write data beyond allocated memory boundaries. An attacker who tricks a user into opening a crafted image file can crash the application or potentially execute arbitrary code on the victim's system.

Technologies: [Strukturag Libheif](https://junglewise.ai/threats/technologies/strukturag-libheif). Vendors: [Strukturag](https://junglewise.ai/threats/vendors/strukturag).

## Quick answers

**Is CVE-2026-84383 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-84383 being exploited in the wild.

**How severe is CVE-2026-84383?** Critical severity, with a CVSS score of 9.8, published 18 September 2026.

**Which products and versions are affected?** Strukturag Libheif 1.22.0 to 1.23.1.

**Is there a fix for CVE-2026-84383?** A patch was published on 2026-08-23: Fixed in version 1.23.2 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-84383 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-84383?** Check whether you run Strukturag Libheif at an affected version. 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

The vulnerability exists in HeifPixelImage::scale_nearest_neighbor() which allocates an 8-bit alpha plane buffer but then writes 10-bit or 12-bit sample values into it when processing nested iden and auxl item references that create duplicate alpha planes with mismatched bit depths. The heap out-of-bounds write is triggered during image decode and is controlled by the image geometry and encoded sample values. This issue is fixed by validating and rejecting duplicate or mismatched-size alpha planes during image decoding.

## Affected products

- strukturag libheif 1.22.0 to 1.23.1

## Timeline

- 2026-09-18: disclosed: Published on NVD
- 2026-08-23: patched: Fixed in version 1.23.2

## References

- [https://github.com/strukturag/libheif/commit/f4fb8bde4704ebb46e46ff9fb94407c9774153b2](https://github.com/strukturag/libheif/commit/f4fb8bde4704ebb46e46ff9fb94407c9774153b2)
- [https://github.com/strukturag/libheif/releases/tag/v1.23.2](https://github.com/strukturag/libheif/releases/tag/v1.23.2)

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- [libheif integer overflow in uncompressed tile range check](https://junglewise.ai/threats/cve-2026-84451-libheif-is-a-heif-and-avif-file-format-decoder-and-encoder-from-1)
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- [libheif reference amplification denial of service](https://junglewise.ai/threats/cve-2026-84447-libheif-is-a-heif-and-avif-file-format-decoder-and-encoder-in-1)