CasApplication · Jenkins
CVE-2021-21673
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 · uneditedJenkins CAS Plugin 1.6.0 and earlier improperly determines that a redirect URL after login is legitimately pointing to Jenkins, allowing attackers to perform 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 confidenceJenkins CAS Plugin 1.6.0 and earlier contains an open redirect vulnerability where the plugin improperly validates redirect URLs after CAS login, allowing attackers to craft malicious URLs that redirect authenticated users to phishing sites instead of legitimate Jenkins locations.
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
CasApplication
<= 1.6.0CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Check if CAS Plugin is installedAccess Jenkins plugin management interface or use Jenkins CLI to list installed plugins and look for 'cas' or 'CAS Plugin' in the listAffected if The CAS Plugin appears in the installed plugins list
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Verify CAS Plugin versionIn Jenkins plugin manager, click on the CAS Plugin to view its details and note the version number displayedAffected if The installed version is 1.6.0 or earlier
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Confirm CAS authentication is configuredNavigate to Jenkins Manage Jenkins > Configure Global Security or Security Realm settings and check if CAS (Central Authentication Service) is set as the security realmAffected if CAS authentication is enabled as the security realm in Jenkins configuration
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Check for existing redirect validationReview the Jenkins CAS Plugin configuration page for any redirect URL validation settingsAffected if No explicit redirect URL validation is configured or the plugin relies solely on client-supplied redirect parameters
You are affected if the Jenkins CAS Plugin version 1.6.0 or earlier is installed AND CAS authentication is enabled as the security realm in your Jenkins configuration.
Generated from the published advisory. Verify against your own configuration.
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 dataUpgrade the Jenkins CAS Plugin to version 1.6.1 or later where the redirect URL validation is properly implemented. If no patched version exists, implement additional server-side validation of redirect URLs before processing.
Fix this in Cas
Scoped from the published advisory
- Consultation2.0 h
- Implementation1.0 h
- Testing3.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,936.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-21673 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-21673 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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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.
- 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