# CVE-2026-5442: Heap Buffer Overflow in DICOM Image Decoder via VR UL Dimensions

> An attacker can trigger a heap buffer overflow in the DICOM decoder via malformed dimensions, potentially leading to code execution or service disruption.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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:** 9 Apr 2026
- **Updated:** 14 Apr 2026
- **Also known as:** DEBIAN-CVE-2026-5442, GHSA-f2m7-r4gw-p642, UBUNTU-CVE-2026-5442

## What is CVE-2026-5442?

CVE-2026-5442 is a critical vulnerability in Orthanc DICOM Server, published on 9 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A heap buffer overflow vulnerability exists in the DICOM image decoder. Dimension fields are encoded using Value Representation (VR) Unsigned Long (UL), instead of the expected VR Unsigned Short (US), which allows extremely large dimensions to be processed. This causes an integer overflow during frame size calculation and results in out-of-bounds memory access during image decoding.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2026-5442?

It affects 1 product.


Products: Orthanc-Server Orthanc.

## How do I fix CVE-2026-5442?

Apply the vendor's patch.

## Is CVE-2026-5442 being exploited?

There is no known exploitation of CVE-2026-5442 in the wild and no public exploit code.

## Other vulnerabilities in Orthanc DICOM Server

- [CVE-2026-5443](https://insights.sbomify.com/CVE-2026-5443/): Heap Buffer Overflow in DICOM Image Decoder (Palette Color Decode) (critical 9.8)
- [CVE-2025-0896](https://insights.sbomify.com/CVE-2025-0896/): Orthanc Server Missing Authentication for Critical Function (critical 9.2)
- [CVE-2026-5445](https://insights.sbomify.com/CVE-2026-5445/): Out-of-Bounds Read in DicomImageDecoder (DecodeLookupTable) (critical 9.1)
- [CVE-2023-33466](https://insights.sbomify.com/CVE-2023-33466/): Path traversal in n/a (high 8.8)
- [CVE-2026-5437](https://insights.sbomify.com/CVE-2026-5437/): Out-of-Bounds Read in DicomStreamReader (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-5442 and fix it if it is affected.

What it is: CVE-2026-5442 is a critical vulnerability in Orthanc DICOM Server, published on 9 Apr 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-2026-5442 in the wild and no public exploit code.

Affected product: Orthanc DICOM Server. 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-2026-5442/ (Markdown: https://insights.sbomify.com/CVE-2026-5442/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-5442
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-5442
- OSV: https://osv.dev/vulnerability/CVE-2026-5442

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-5442/
Summaries are generated and may contain mistakes; the official description above is the record.