dbcve.org
Velocity.jsApplication · Shepherdwind

CVE-2026-44966

CRITICAL · 9.8 CVSS v3.1 Published 2026-05-26
Fix available
A fix is available. Upgrade to after 2.1.5 or later.
See remediation →
100/100
Remediation priority · Urgent
Public exploit 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
Velocity.js is a JavaScript implementation of the Apache Velocity template engine. In 2.1.5 and earlier, a prototype pollution vulnerability was discovered in velocityjs. This issue occurs during the processing of #set directives in Velocity templates. If an application renders a template controlled by an attacker, it is possible to modify Object.prototype, potentially leading to Denial of Service (DoS) or Remote Code Execution (RCE) depending on the server environment.

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

Prototype pollution vulnerability in Velocity.js versions 2.1.5 and earlier allows attackers to modify Object.prototype through malicious #set directives in Velocity templates, potentially leading to DoS or RCE when applications render attacker-controlled templates.

MitigationUpgrade to a patched version of velocityjs if available; otherwise, implement strict input validation/sanitization to prevent untrusted users from controlling template content with #set directives.

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
Velocity.jsApplication
Affected:<= 2.1.5

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
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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 velocityjs installation
    Check package.json dependencies, node_modules folder, or any JavaScript file that imports velocityjs using require('velocityjs') or import statements
    Affected if velocityjs is present in the project dependencies or runtime environment
  2. Determine installed version
    Run npm list velocityjs or check package.json for the velocityjs version number, then compare against 2.1.5
    Affected if The installed version is 2.1.5 or lower
  3. Locate template files using #set directives
    Search project codebase for .vm template files or template strings containing #set syntax, or inspect runtime template storage
    Affected if Templates containing #set directives are found in the application
  4. Determine if templates are user-controlled
    Review code paths that render Velocity templates to identify if template content originates from user input, API requests, databases, or external sources without validation
    Affected if Templates are sourced from untrusted input or user-controlled sources such as request parameters, uploaded files, or database records
  5. Verify #set processing is active
    Trace code execution to confirm that the #set directive is actually processed at runtime when rendering user-supplied templates
    Affected if The application renders templates with #set directives from untrusted sources without sanitization

The environment is affected if velocityjs version 2.1.5 or lower is installed AND user-controlled templates containing #set directives are rendered without input validation or sandboxing.

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 a release after 2.1.5
Interim mitigation

Upgrade to a patched version of velocityjs if available; otherwise, implement strict input validation/sanitization to prevent untrusted users from controlling template content with #set directives.

Recommended fix Moderate confidence

velocityjs version 2.1.6 or latest available release

  1. 1. Check the current version of velocityjs in your project by running: npm list velocityjs
  2. 2. Review your application's template rendering code to identify where user-controlled input is passed to Velocity.js #set directives
  3. 3. Upgrade velocityjs to the latest version available on npm: npm install velocityjs@latest
  4. 4. Alternatively, upgrade to a specific version known to contain the fix (check GitHub releases for version 2.1.6 or later): npm install [email protected]
  5. 5. After upgrading, test your application to ensure templates render correctly and the vulnerability is remediated
  6. 6. Verify no other template engines or libraries in your project are vulnerable to similar prototype pollution issues
Caveat Review velocityjs release notes for any breaking changes between your current version and the fixed version

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

Fix this in Velocity.js Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing8.0 h
  • Review / QA3.0 h
20.0 hours of engineering $3,420
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,472.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2026-44966 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2026-44966 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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