CVE-2026-5438: Orthanc-Server Orthanc

High severity, CVSS 7.5. EPSS: 0.8% chance of exploitation in the next 30 days.

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.

Affected products

• Orthanc-Server Orthanc: before 1.12.11 (fixed in 1.12.11)

Published 2026-04-09. Last modified 2026-06-17.