# CVE-2026-32738: libheif has a Heap OOB Read/SEGV Crash via Zero samples_per_chunk

> A crafted HEIF file triggers an integer underflow leading to a null-pointer dereference and crash, causing denial of service in libheif.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 19 May 2026
- **Updated:** 19 May 2026
- **Also known as:** ALPINE-CVE-2026-32738, BELL-CVE-2026-32738, DEBIAN-CVE-2026-32738, GHSA-7f2h-cmpf-v9ww, JLSEC-2026-570, ROOT-OS-DEBIAN-12-CVE-2026-32738, UBUNTU-CVE-2026-32738

## What is CVE-2026-32738?

CVE-2026-32738 is a medium-severity vulnerability in strukturag libheif, published on 19 May 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 versions 1.21.2 and below, a crafted 792-byte HEIF sequence file with samples_per_chunk=0 in the stsc box causes an unsigned integer underflow in the Chunk constructor (m_last_sample = 0 + 0 - 1 = UINT32_MAX), mapping all samples to an empty chunk and resulting in a denial of service. When any sample is accessed, the library reads from index 0 of an empty std::vector, causing a guaranteed SEGV (null-page read). The file parses successfully without producing an error; the crash occurs on the first frame access. This issue has been fixed in version 1.22.0.

Weakness: CWE-476 (NULL Pointer Dereference), CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-32738?

It affects 1 product.


Products: Struktur Libheif.

## How do I fix CVE-2026-32738?

Upgrade to a fixed version.

## Is CVE-2026-32738 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-32738 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-2026-32738 and fix it if it is affected.

What it is: CVE-2026-32738 is a medium-severity vulnerability in strukturag libheif, published on 19 May 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: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-32738 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-2026-32738/ (Markdown: https://insights.sbomify.com/CVE-2026-32738/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-32738
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-32738
- OSV: https://osv.dev/vulnerability/CVE-2026-32738

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-32738/
Summaries are generated and may contain mistakes; the official description above is the record.