# CVE-2026-120208: libheif heap buffer overflow in unc_decoder_mixed_interleave

Source: https://junglewise.ai/threats/cve-2026-120208-libheif-1-18-0-before-1-23-3-contains-a-heap-based-buffer  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-31. Updated: 2026-10-31  
License: CC BY 4.0 with a link back

CVE-2026-120208 · Severity: high · CVSS 7.5 · Published 2026-10-31

libheif is a library for encoding and decoding High Efficiency Image Format (HEIF) files, commonly used in image processing and media applications. A heap buffer overflow in the uncompressed image decoder allows attackers who craft malicious HEIF files with mismatched chroma bit depths to write out of bounds and potentially execute code when the image is processed.

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

## Quick answers

**Is CVE-2026-120208 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-120208 being exploited in the wild.

**How severe is CVE-2026-120208?** High severity, with a CVSS score of 7.5, published 31 October 2026.

**Which products and versions are affected?** Strukturag Libheif 1.18.0 before 1.23.3.

**Is there a fix for CVE-2026-120208?** Yes: fixed in libheif 1.23.3. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-120208 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-120208?** 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.

## How to fix

- Fixed in libheif 1.23.3

## Technical details

A heap-based buffer overflow exists in unc_decoder_mixed_interleave::processTile() when decoding uncompressed HEIF images with mixed-interleave chroma sampling. The decoder incorrectly uses a single byte width for both Cb and Cr chroma planes when they are declared with different bit depths (e.g., 16-bit Cb and 8-bit Cr), causing writes to the smaller plane to overflow into adjacent heap memory. An attacker can craft a HEIF file to trigger file-controlled out-of-bounds writes.

## Affected products

- strukturag libheif 1.18.0 before 1.23.3

## Timeline

- 2026-10-31: disclosed
- 2026-08-31: patched: commit 9d3cd91 merged

## References

- [https://github.com/strukturag/libheif/blob/v1.23.2/libheif/codecs/uncompressed/unc_decoder_mixed_interleave.cc](https://github.com/strukturag/libheif/blob/v1.23.2/libheif/codecs/uncompressed/unc_decoder_mixed_interleave.cc)
- [https://github.com/strukturag/libheif/commit/9d3cd91d7b1c8c68deef6d06057ab956bcb0dfb9](https://github.com/strukturag/libheif/commit/9d3cd91d7b1c8c68deef6d06057ab956bcb0dfb9)

## Related threats

- [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)
- [libheif assertion failure in clap property crop calculation](https://junglewise.ai/threats/cve-2026-84450-libheif-is-a-heif-and-avif-file-format-decoder-and-encoder-from-1)
- [libheif heap out-of-bounds read in inline-mask region API](https://junglewise.ai/threats/cve-2026-84448-libheif-is-a-heif-and-avif-file-format-decoder-and-encoder-prior)
- [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)
- [libheif sequence timing denial of service and memory exhaustion](https://junglewise.ai/threats/cve-2026-84446-libheif-is-a-heif-and-avif-file-format-decoder-and-encoder-prior)