# CVE-2026-62291 — strukturag libheif

> As of 2026-08-18, CVE-2026-62291 is a MEDIUM-severity vulnerability in strukturag libheif, CVSS v3.1 5.3, EPSS 0.1% (5.9th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-62291 as of 2026-08-18; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-08-18

## What is CVE-2026-62291?

libheif is a HEIF and AVIF file format decoder and encoder. In 1.23.0 and earlier, a crafted image sequence with a 2x2 primary plane and a 256x256 auxiliary alpha plane can cause attacker-controlled heap corruption during a normal decode and re-encode workflow. Track_Visual::decode_next_image_sample() calls transfer_channel_from_image_as() without checking that the auxiliary alpha dimensions match the main frame. The resulting inconsistent image reaches heif_track_decode_next_image() and then heif_context_encode_image(). In unc_encoder::encode(), unc_encoder_component_interleave::encode_tile() sizes its buffer with compute_tile_data_size_bytes() using the primary dimensions but copies each component using its actual plane dimensions. The oversized alpha plane is therefore copied beyond the allocation, causing an out-of-bounds write; the inverse size mismatch can also produce an out-of-bounds read. This issue is fixed in version 1.23.1.

The record classifies CVE-2026-62291 under weakness classes [CWE-125](https://intel.threadlinqs.com/cwe/CWE-125), [CWE-787](https://intel.threadlinqs.com/cwe/CWE-787). Its CVSS v3 base vector states that the flaw requires local access to the host, needs no prior authentication, needs a user to take an action first. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 48 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 5.3 — MEDIUM (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L`)
- **EPSS (FIRST):** 0.1% probability of exploitation in the next 30 days, higher than 5.9% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 4.9/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-08-18

## Is CVE-2026-62291 being exploited?

Weaponised exploit code for CVE-2026-62291 is publicly available. 1 public proof-of-concept repository is tracked for this identifier. It currently carries a trending score of 39 in the Threadlinqs vulnerability feed.

- [trickest/cve](https://github.com/trickest/cve/blob/main/2026/CVE-2026-62291.md) (trickest)

## Affected products and versions

- **strukturag**: libheif

## How to fix CVE-2026-62291

No vendor patch reference has been recorded for CVE-2026-62291 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-62291

No threat campaign in the Threadlinqs corpus currently references CVE-2026-62291, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, NVD, FIRST EPSS, public proof-of-concept repositories. Last verified by Threadlinqs on 2026-08-19. This product uses the NVD API but is not endorsed or certified by the NVD.

**Vendor advisory and patch**

- [github.com](https://github.com/strukturag/libheif/security/advisories/GHSA-xpw3-9rhw-482x)

**Other references**

- [github.com](https://github.com/strukturag/libheif/commit/ac5521ad50399885de96bb6a0733a5d2442740f9)
- [github.com (v1.23)](https://github.com/strukturag/libheif/releases/tag/v1.23.1)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-62291
Full detection coverage and IOCs for threats exploiting CVE-2026-62291 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp