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Velocity ToolsApplication · Apache

CVE-2020-13959

MEDIUM · 6.1 CVSS v3.1 Published 2021-03-10
Fix available
A fix is available. Upgrade to 3.1 or later.
See remediation →
68/100
Remediation priority · Elevated
Remotely reachable No privileges

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
The default error page for VelocityView in Apache Velocity Tools prior to 3.1 reflects back the vm file that was entered as part of the URL. An attacker can set an XSS payload file as this vm file in the URL which results in this payload being executed. XSS vulnerabilities allow attackers to execute arbitrary JavaScript in the context of the attacked website and the attacked user. This can be abused to steal session cookies, perform requests in the name of the victim or for phishing attacks.

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

Reflected XSS vulnerability in Apache Velocity Tools' VelocityView component. When an invalid .vm template file is requested, the default error page reflects the filename parameter back without sanitization, allowing arbitrary JavaScript execution via a crafted URL.

MitigationUpgrade to Apache Velocity Tools version 3.1 or later. Until upgraded, implement input validation on URL parameters and output encoding on the error page to neutralize malicious payloads.

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 ToolsApplication
Affected:< 3.1
Debian LinuxOperating system
Affected:= 9.0

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
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

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

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 VelocityView is in use
    Examine the application's web.xml file for the VelocityViewServlet or VelocityViewFilter configuration, or check the application's classpath for velocity-tools JAR files.
    Affected if VelocityViewServlet or VelocityViewFilter is configured and exposed via web
  2. Determine Apache Velocity Tools version
    Locate the velocity-tools JAR file in the application's lib directory or classpath and check its version (typically velocity-tools-x.x.jar). Compare the version number against the affected range (versions prior to 3.1 are vulnerable).
    Affected if The installed version of Apache Velocity Tools is lower than 3.1
  3. Verify .vm template access via web
    Determine whether .vm template files are accessible through the web server. Check the servlet mapping for VelocityView and try accessing a .vm file through the application URL.
    Affected if .vm templates are served directly via web and the VelocityView component handles them
  4. Test for reflected XSS in error page
    Request an invalid .vm template file via a crafted URL parameter (for example, append ?file=<filename>.vm where the filename contains a test XSS payload such as <script>alert(1)</script>). Inspect whether the error response reflects the payload unsanitized.
    Affected if The error page reflects the filename parameter value without encoding

A user is affected if Apache Velocity Tools version is below 3.1 AND VelocityView is deployed with .vm templates accessible via web, allowing the error page to reflect unsanitized filename input.

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.

From vendor data
Upgrade available Upgrade to 3.1 or later
Fixed in 3.1
Interim mitigation

Upgrade to Apache Velocity Tools version 3.1 or later. Until upgraded, implement input validation on URL parameters and output encoding on the error page to neutralize malicious payloads.

Fix this in Velocity Tools Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing3.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,750
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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-2020-13959 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