# CVE-2026-5439: Memory Exhaustion via Forged ZIP Metadata

> Attackers can cause server memory exhaustion and denial of service by uploading crafted ZIP archives with forged size metadata to Orthanc DICOM server.

- **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:** 9 Apr 2026
- **Updated:** 14 Apr 2026
- **Also known as:** DEBIAN-CVE-2026-5439, GHSA-6cmv-pvcc-pf5h, UBUNTU-CVE-2026-5439

## What is CVE-2026-5439?

CVE-2026-5439 is a high-severity denial of service 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 memory exhaustion vulnerability exists in ZIP archive processing. Orthanc automatically extracts ZIP archives uploaded to certain endpoints and trusts metadata fields describing the uncompressed size of archived files. An attacker can craft a small ZIP archive containing a forged size value, causing the server to allocate extremely large buffers during extraction.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2026-5439?

It affects 1 product.


Products: Orthanc-Server Orthanc.

## How do I fix CVE-2026-5439?

Apply the vendor's patch.

## Is CVE-2026-5439 being exploited?

There is no known exploitation of CVE-2026-5439 in the wild and no public exploit code.

## Other vulnerabilities in Orthanc DICOM Server

- [CVE-2026-5442](https://insights.sbomify.com/CVE-2026-5442/): Heap Buffer Overflow in DICOM Image Decoder via VR UL Dimensions (critical 9.8)
- [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)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-5439 and fix it if it is affected.

What it is: CVE-2026-5439 is a high-severity denial of service 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-2026-5439 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-2026-5439/ (Markdown: https://insights.sbomify.com/CVE-2026-5439/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-5439
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-5439
- OSV: https://osv.dev/vulnerability/CVE-2026-5439

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-5439/
Summaries are generated and may contain mistakes; the official description above is the record.