# CVE-2026-62289: libheif: Integer underflow in Fraction constructor via double clap transform application

> A crafted HEIF or AVIF file triggers an integer underflow in libheif, causing crashes or corrupt tiling results during image processing.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 18 Aug 2026
- **Updated:** 19 Aug 2026
- **Also known as:** BELL-CVE-2026-62289, DEBIAN-CVE-2026-62289, ECHO-ebfc-8101-ce00, GHSA-jc8f-p23p-5hjg, MINI-cmf9-rwvq-rc53

## What is CVE-2026-62289?

CVE-2026-62289 is a medium-severity vulnerability in strukturag libheif, published on 18 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

libheif is a HEIF and AVIF file format decoder and encoder. In 1.23.0 and earlier, a crafted HEIF or AVIF file containing a clean aperture box can reduce an image dimension to zero and crash or corrupt tiling results when heif_image_handle_get_image_tiling(handle, 1, &tiling) is called. ImageItem::get_heif_image_tiling() returns already transformed dimensions, and process_image_transformations_on_tiling() applies the clean aperture transformation again. The second application passes zero to Box_clap::left_rounded(0), where image_width minus one underflows and constructs Fraction(0xFFFFFFFF, 2). Debug builds reach an assertion and abort, while release builds can return a corrupt crop and zero-width tiling result. The affected implementation spans libheif/image-items/image_item.cc, libheif/context.cc, and libheif/box.cc. This issue is fixed in version 1.23.1.

Weakness: CWE-617 (Reachable Assertion), CWE-191 (Integer Underflow (Wrap or Wraparound))

## Which versions are affected by CVE-2026-62289?


## How do I fix CVE-2026-62289?

Upgrade to a fixed version.

## Is CVE-2026-62289 being exploited?

There is no known exploitation of CVE-2026-62289 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-62289 and fix it if it is affected.

What it is: CVE-2026-62289 is a medium-severity vulnerability in strukturag libheif, published on 18 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-62289 in the wild and no public exploit code.

Affected product: strukturag libheif. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-62289/ (Markdown: https://insights.sbomify.com/CVE-2026-62289/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-62289
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-62289
- OSV: https://osv.dev/vulnerability/CVE-2026-62289

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-62289/
Summaries are generated and may contain mistakes; the official description above is the record.