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OrthancApplication · Orthanc Server

CVE-2026-5440

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 the HTTP server due to unbounded use of the `Content-Length` header. The server allocates memory directly based on the attacker supplied header value without enforcing an upper limit. A crafted HTTP request containing an extremely large `Content-Length` value can trigger excessive memory allocation and server termination, even without sending a request body.

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 · high confidence

The HTTP server allocates memory based on the Content-Length header value supplied by the client without enforcing any upper bound. An attacker can send a request with an extremely large Content-Length value (e.g., 10GB) causing the server to attempt allocating that much memory, leading to memory exhaustion and service termination. The attack succeeds even without sending the actual request body.

MitigationImplement a maximum allowed Content-Length limit configured per-endpoint or globally, rejecting requests that exceed this threshold before any memory allocation occurs.

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 if Orthanc Server is running
    Check for running Orthanc processes or listening ports (typically port 8042 for the HTTP UI)
    Affected if Orthanc HTTP server is exposed and accessible on the network
  2. Determine installed Orthanc version
    Run 'orthanc --version' or check the Orthanc UI footer, or query the /system API endpoint
    Affected if Version is below 1.12.11 (the affected range is any version prior to 1.12.11)
  3. Verify HTTP server is enabled
    Check Orthanc configuration for 'HttpPort' or 'HttpEnabled' settings in orthanc.json
    Affected if HTTP server is enabled and accepting connections
  4. Inspect Content-Length configuration
    Review orthanc.json for any 'HttpMaxContentLength' or similar limit settings
    Affected if No upper bound on Content-Length is configured, allowing arbitrary header values to trigger memory allocation

You are affected if Orthanc Server with an exposed HTTP interface is running at a version lower than 1.12.11 and has no Content-Length limit configured, allowing an attacker to trigger memory exhaustion via a large Content-Length header.

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 a maximum allowed Content-Length limit configured per-endpoint or globally, rejecting requests that exceed this threshold before any memory allocation occurs.

Recommended fix High confidence

Orthanc 1.12.11 or later

  1. 1. Backup your current Orthanc configuration and any custom plugins
  2. 2. Download Orthanc version 1.12.11 or later from the official Orthanc download page (www.orthanc-server.com)
  3. 3. Install the new version following the standard installation procedure for your platform
  4. 4. Restore your backed-up configuration files
  5. 5. Restart the Orthanc service
  6. 6. Verify the server is running and responsive with a test HTTP request
  7. 7. Confirm memory usage remains stable even with large Content-Length values in requests

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

Fix this in Orthanc Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,088.

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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-2026-5440 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data