# CVE-2026-50142: libheif: unbounded heap allocation in HEIF sequence parser (stsz fixed-size mode missing bound check)

> A crafted HEIF file can cause unbounded heap allocation and memory exhaustion in libheif, leading to a denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Aug 2026
- **Updated:** 19 Aug 2026
- **Also known as:** ALPINE-CVE-2026-50142, BELL-CVE-2026-50142, DEBIAN-CVE-2026-50142, GHSA-jvmp-j3cw-84mh, MINI-9mgj-9mwg-95c2, ROOT-OS-DEBIAN-12-CVE-2026-50142, UBUNTU-CVE-2026-50142

## What is CVE-2026-50142?

CVE-2026-50142 is a high-severity denial of service vulnerability in strukturag libheif, published on 18 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

libheif is a HEIF and AVIF file format decoder and encoder. From 1.19.0 until 1.23.0, a crafted HEIF sequence accepted by heif_context_read_from_memory() with the msf1 sequence brand can cause unbounded heap allocation. In libheif/sequences/seq_boxes.cc, Box_stsz::parse() applies max_sequence_frames only to variable-size samples, so fixed-size mode accepts an attacker-controlled sample_count without a bound. In libheif/sequences/track.cc, Track::load() also adds current_sample_idx and samples_per_chunk in 32-bit arithmetic, allowing the consistency check to be bypassed by wraparound. The resulting values reach the Chunk::Chunk() allocation path, which can consume gigabytes of memory and crash or stall the process through memory exhaustion. This issue is fixed in version 1.23.0.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling), CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2026-50142?


## How do I fix CVE-2026-50142?

Upgrade to a fixed version.

## Is CVE-2026-50142 being exploited?

There is no known exploitation of CVE-2026-50142 in the wild and no public exploit code.

Public exploit code:

- CVE-2026-50142 — Heap allocation vulnerability in libheif HEIF sequence parser (github_poc): https://github.com/MuhammedHussein17/libheif-cve-2026-50142

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-50142 and fix it if it is affected.

What it is: CVE-2026-50142 is a high-severity denial of service vulnerability in strukturag libheif, published on 18 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-50142 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-2026-50142/ (Markdown: https://insights.sbomify.com/CVE-2026-50142/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-50142
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-50142
- OSV: https://osv.dev/vulnerability/CVE-2026-50142

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-50142/
Summaries are generated and may contain mistakes; the official description above is the record.