CVE-2020-5409
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 · uneditedPivotal Concourse, most versions prior to 6.0.0, allows redirects to untrusted websites in its login flow. A remote unauthenticated attacker could convince a user to click on a link using the OAuth redirect link with an untrusted website and gain access to that user's access token in Concourse. (This issue is similar to, but distinct from, CVE-2018-15798.)
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 confidencePivotal Concourse versions prior to 6.0.0 contain an open redirect vulnerability in its OAuth login flow. An unauthenticated remote attacker can craft malicious links with untrusted redirect URIs in the OAuth authorization request, causing users' access tokens to be sent to attacker-controlled websites instead of the legitimate Concourse instance.
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< 5.2.8>= 5.3.0, < 5.5.10>= 5.6.0, < 5.8.1CVSS 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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Identify Concourse versionRetrieve the installed Concourse version from the web UI footer, the 'fly --version' command, or the deployment configuration. Compare it against the affected ranges: < 5.2.8, >= 5.3.0 and < 5.5.10, >= 5.6.0 and < 5.8.1.Affected if The installed version falls within any of the listed affected ranges and is earlier than 6.0.0.
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Determine if OAuth login is enabledReview the Concourse deployment manifest or configuration files for OAuth-related settings such as 'github', 'generic-oauth', 'gitlab', or other OAuth provider configurations under the 'atc' section.Affected if OAuth authentication is configured and active for the Concourse instance.
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Inspect OAuth redirect URI configurationExamine the OAuth provider configuration for the 'redirect_uri' or 'redirect' parameter. Check whether the configuration allows arbitrary or externally-controlled redirect URIs rather than restricting to a fixed list of trusted domains.Affected if The redirect URI is not strictly constrained to a known trusted domain or includes user-supplied input.
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Review allowed redirect domainsLook for parameters such as 'auth-url', 'skip-ssl-validation', or any setting that defines allowed callback endpoints in the OAuth provider block. Verify if the configuration explicitly lists permitted redirect domains or permits open redirects.Affected if The configuration permits redirect URIs outside the trusted Concourse domain.
If the Concourse version is in the affected range (< 6.0.0) and OAuth authentication is enabled with insufficiently validated redirect URIs, the instance is vulnerable to CVE-2020-5409.
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 data5.2.85.5.105.8.1
Upgrade to Concourse 6.0.0 or later which properly validates OAuth redirect URIs. If immediate upgrade is not possible, review and restrict allowed redirect URIs in the OAuth provider configuration to only trusted domains.
- Consultation3.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2020-5409 — 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-2020-5409 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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- Version or environment caveats, and links to real fixes
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