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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
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
Which versions are affected by CVE-2026-5439?
It affects 1 product.
Products include Orthanc-Server Orthanc.
How do I fix CVE-2026-5439?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
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 Heap Buffer Overflow in DICOM Image Decoder via VR UL Dimensions
- CVE-2026-5443 Heap Buffer Overflow in DICOM Image Decoder (Palette Color Decode)
- CVE-2025-0896 Orthanc Server Missing Authentication for Critical Function
- CVE-2026-5445 Out-of-Bounds Read in DicomImageDecoder (DecodeLookupTable)
- CVE-2023-33466 Path traversal in n/a
Sources
Also known as DEBIAN-CVE-2026-5439, GHSA-6cmv-pvcc-pf5h, UBUNTU-CVE-2026-5439.