Memory Exhaustion in Orthanc ZIP Processing via Forged Metadata

Publication date: 2026-04-09

Last updated on: 2026-04-15

Assigner: CERT/CC

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.

CVSS Scores

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Meta Information

Published

2026-04-09

Last Modified

2026-04-15

Generated

2026-07-06

AI Q&A

2026-04-09

EPSS Evaluated

2026-07-05

NVD

CVE-2026-5439

EUVD

EUVD-2026-20916

Affected Vendors & Products

Vendor	Product	Version / Range
orthanc-server	orthanc	to 1.12.11 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-770	The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

Attack-Flow Graph

Executive Summary

This vulnerability is a memory exhaustion issue in the processing of ZIP archives by Orthanc. When Orthanc automatically extracts ZIP archives uploaded to certain endpoints, it relies on metadata fields that describe the uncompressed size of the files inside the archive. An attacker can create a small ZIP archive with a forged size value that is much larger than the actual content, causing the server to allocate very large buffers during extraction.

Impact Analysis

The impact of this vulnerability is that an attacker can cause the server to allocate excessive memory resources by submitting a crafted ZIP archive. This can lead to memory exhaustion, potentially causing the server to slow down, crash, or become unresponsive, resulting in a denial of service.

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