# CVE-2026-84450: libheif: `clap` + oversized `ispe` aborts on an assert in `Fraction::Fraction` (incomplete fix for CVE-2026-62289)

> A crafted HEIF/AVIF image can cause an application using libheif to abort due to an assertion failure during crop calculations.

- **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 Sep 2026
- **Updated:** 21 Sep 2026
- **Also known as:** BELL-CVE-2026-84450, DEBIAN-CVE-2026-84450, ECHO-2ec0-a051-6be2, GHSA-gh5q-69gg-c964, MINI-g6g2-975r-673h

## What is CVE-2026-84450?

CVE-2026-84450 is a medium-severity denial of service vulnerability in strukturag libheif, published on 18 Sep 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. From 1.19.0 until 1.23.3, a crafted image item containing a clap property and an ispe width or height greater than INT32_MAX + 1 can reach crop calculations through heif_image_handle_get_image_tiling(). Box_clap::left_rounded() or Box_clap::top_rounded() passes the image dimension minus one to Fraction::Fraction(), whose uint32_t constructor uses an assertion as input validation, causing assert-enabled builds to abort. Release builds can instead compute invalid crop geometry, and the tiling API returns dimensions that the normal decode security limits reject. This issue is fixed in version 1.23.3.

Weakness: CWE-617 (Reachable Assertion)

## Which versions are affected by CVE-2026-84450?


## How do I fix CVE-2026-84450?

Upgrade to a fixed version.

## Is CVE-2026-84450 being exploited?

There is no known exploitation of CVE-2026-84450 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-84450 and fix it if it is affected.

What it is: CVE-2026-84450 is a medium-severity denial of service vulnerability in strukturag libheif, published on 18 Sep 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-2026-84450 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-2026-84450/ (Markdown: https://insights.sbomify.com/CVE-2026-84450/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-84450
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-84450
- OSV: https://osv.dev/vulnerability/CVE-2026-84450

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-84450/
Summaries are generated and may contain mistakes; the official description above is the record.