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OrthancApplication · Orthanc Server

CVE-2026-5439

HIGH · 7.5 CVSS v3.1 Published 2026-04-09
Fix available
A fix is available. Upgrade to 1.12.11 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

Orthanc contains a memory exhaustion vulnerability in its ZIP archive processing. The application automatically extracts ZIP archives uploaded to certain endpoints and trusts the uncompressed size metadata provided within the archive without validation. An attacker can craft a small ZIP file containing a forged uncompressed size value, causing the server to attempt allocating extremely large buffers during extraction, leading to denial of service.

MitigationImplement bounds validation on ZIP metadata by verifying uncompressed sizes against actual extracted data or configurable limits, and use streaming extraction instead of pre-allocating buffers based on untrusted metadata.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
OrthancApplication
Affected:< 1.12.11

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify the installed Orthanc version
    Run 'Orthanc --version' or check the Orthanc configuration file/header for the version number, typically displayed in server logs or the /system endpoint
    Affected if The installed version is lower than 1.12.11
  2. Determine if ZIP archive upload endpoints are enabled
    Review Orthanc configuration for enabled HTTP endpoints that accept file uploads, specifically those that process ZIP archives such as /tools/create-archive or similar upload routes
    Affected if ZIP upload or archive creation endpoints are accessible and enabled
  3. Verify if the server accepts unauthenticated ZIP uploads
    Check Orthanc authentication settings and network exposure - determine if remote unauthenticated users can POST ZIP files to the server
    Affected if The server allows unauthenticated or untrusted users to upload ZIP archives to processing endpoints
  4. Inspect server memory behavior during ZIP processing
    Monitor server memory usage when processing ZIP files - observe if memory consumption spikes disproportionately relative to the uploaded file size
    Affected if Memory usage grows excessively or causes resource exhaustion when processing small ZIP files with large declared uncompressed sizes

The environment is affected if Orthanc version is below 1.12.11 and the server exposes accessible ZIP archive upload endpoints to users or processes untrusted ZIP files.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 1.12.11 or later
Fixed in 1.12.11
Interim mitigation

Implement bounds validation on ZIP metadata by verifying uncompressed sizes against actual extracted data or configurable limits, and use streaming extraction instead of pre-allocating buffers based on untrusted metadata.

Recommended fix High confidence

Orthanc 1.12.11 or later

  1. 1. Back up the current Orthanc configuration and database
  2. 2. Identify the current Orthanc version running (check /about endpoint or version log)
  3. 3. Download Orthanc version 1.12.11 or later from the official Orthanc server download page (https://www.orthanc-server.com/download/)
  4. 4. Stop the Orthanc service
  5. 5. Replace the Orthanc executable and any associated libraries with the new version
  6. 6. Restore the backed-up configuration
  7. 7. Start the Orthanc service
  8. 8. Verify the version has been updated to 1.12.1 or later
Caveat Review release notes for 1.12.11 to check for any configuration or API changes that may affect existing integrations

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Orthanc Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-5439 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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