# CVE-2026-47251: libheif has an incomplete fix for CVE-2026-3949: integer overflow bypass in vvdec_push_data2

> An integer overflow in libheif's security check allows crafted HEIF files to trigger out-of-bounds heap reads, potentially causing crashes or data leaks.

- **Severity:** Medium 6.8 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 21 Jul 2026
- **Updated:** 22 Jul 2026
- **Also known as:** BELL-CVE-2026-47251, ECHO-1888-e250-4427, GHSA-p6q9-fhf2-vj9v, JLSEC-2026-1097

## What is CVE-2026-47251?

CVE-2026-47251 is a medium-severity vulnerability in strukturag libheif, published on 21 Jul 2026. It can only be exploited from the same machine or local network, 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. The fix for CVE-2026-3949 (commit `b97c8b5`, PR #1712) introduced an integer overflow in the very security check it added. The check itself can be bypassed, allowing a crafted HEIF file with a VVC track to trigger the same out-of-bounds heap read that CVE-2026-3949 was meant to prevent. This is a separate, currently-unpatched vulnerability. Issue #1712 was closed as fixed without testing the edge case where `size` is near `UINT32_MAX`. Version 1.22.0 patches the issue.

Weakness: CWE-190 (Integer Overflow or Wraparound), CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-47251?

It affects 1 product.


Products: Struktur Libheif.

## How do I fix CVE-2026-47251?

Upgrade to a fixed version.

## Is CVE-2026-47251 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-47251 exists.

## Other vulnerabilities in strukturag libheif

- [CVE-2026-32740](https://insights.sbomify.com/CVE-2026-32740/): libheif: Heap-Buffer-Overflow Write in Grid Tile Chroma Compositing (high 8.8)
- [CVE-2023-49460](https://insights.sbomify.com/CVE-2023-49460/): Null dereference in n/a (high 8.8)
- [CVE-2023-49462](https://insights.sbomify.com/CVE-2023-49462/): Null dereference in n/a (high 8.8)
- [CVE-2023-49463](https://insights.sbomify.com/CVE-2023-49463/): Null dereference in n/a (high 8.8)
- [CVE-2023-49464](https://insights.sbomify.com/CVE-2023-49464/): Null dereference in n/a (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-47251 and fix it if it is affected.

What it is: CVE-2026-47251 is a medium-severity vulnerability in strukturag libheif, published on 21 Jul 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-47251 exists.

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-2026-47251/ (Markdown: https://insights.sbomify.com/CVE-2026-47251/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-47251
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-47251
- OSV: https://osv.dev/vulnerability/CVE-2026-47251

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-47251/
Summaries are generated and may contain mistakes; the official description above is the record.