CVE-2026-5438 Gzip Decompression Bomb via Content-Encoding Header
Attackers can cause memory exhaustion and denial of service in Orthanc DICOM Server by sending crafted gzip payloads via HTTP requests.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-5438?
CVE-2026-5438 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 gzip decompression bomb vulnerability exists when Orthanc processes HTTP request with `Content-Encoding: gzip`. The server does not enforce limits on decompressed size and allocates memory based on attacker-controlled compression metadata. A specially crafted gzip payload can trigger excessive memory allocation and exhaust system memory.
Weakness: CWE-770
Which versions are affected by CVE-2026-5438?
It affects 1 product.
Products include Orthanc-Server Orthanc.
How do I fix CVE-2026-5438?
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-2026-5438 being exploited?
There is no known exploitation of CVE-2026-5438 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-2026-5438, GHSA-7vj5-pm38-6wjv, UBUNTU-CVE-2026-5438.