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ConcourseApplication · Pivotal Software

CVE-2020-5415

CRITICAL · 10.0 CVSS v3.1 Published 2020-08-12
Fix available
A fix is available. Upgrade to 6.3.1 / 6.4.1 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click Patch available

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
Concourse, versions prior to 6.3.1 and 6.4.1, in installations which use the GitLab auth connector, is vulnerable to identity spoofing by way of configuring a GitLab account with the same full name as another user who is granted access to a Concourse team. GitLab groups do not have this vulnerability, so GitLab users may be moved into groups which are then configured in the Concourse team.

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

Concourse's GitLab auth connector uses full names as a primary identity attribute for authorization. An attacker can register a GitLab account with the same full name as an existing authorized user to impersonate them and gain unauthorized access to Concourse teams. This occurs because the connector does not uniquely identify users beyond their display name.

MitigationUpgrade to Concourse 6.3.1 or 6.4.1 and later. Alternatively, migrate from individual GitLab user assignments to GitLab group-based team membership, which is not vulnerable to this spoofing issue.

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
ConcourseApplication
Affected:< 6.3.1>= 6.4.0, < 6.4.1

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
Changed
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/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. Confirm GitLab auth connector is in use
    Inspect your Concourse web node configuration for the --gitlab-auth-* flags or the corresponding YAML/credentials file. Look for presence of --gitlab-client-id and --gitlab-client-secret flags or GitLab-related auth configuration.
    Affected if GitLab authentication is configured and enabled on this Concourse deployment
  2. Check Concourse version
    Run 'concourse --version' on the web node or check the Docker/container image tag. Compare the version against the affected ranges: < 6.3.1 or >= 6.4.0 and < 6.4.1.
    Affected if The installed version falls within the vulnerable version ranges
  3. Verify user identity attribute configuration
    Review the GitLab auth connector configuration in the main Concourse config or environment variables. Look for how the 'user_id' or 'username' attribute is mapped. Check if it references the 'display_name' or full name field from GitLab instead of a unique identifier like 'id' or 'username'.
    Affected if The configuration maps user identity using display_name or full_name from GitLab rather than a unique identifier
  4. Review team user assignments
    Run 'fly teams -t <target>' to list teams, then check which users are authorized. Cross-reference GitLab user accounts with their display names. Look for teams that have individual GitLab users granted access.
    Affected if Individual GitLab users are assigned to teams based on their full display names rather than GitLab group memberships

You are affected if your Concourse version is vulnerable AND you use GitLab authentication with user identity mapped to full display names instead of unique identifiers, allowing an attacker to spoof by registering with a matching full name.

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 6.3.1 / 6.4.1 or later
Fixed in 6.3.16.4.1
Vendor patch github.com →
Interim mitigation

Upgrade to Concourse 6.3.1 or 6.4.1 and later. Alternatively, migrate from individual GitLab user assignments to GitLab group-based team membership, which is not vulnerable to this spoofing issue.

Recommended fix High confidence

Concourse 6.3.1 or 6.4.1 (depending on your current major.minor version)

  1. Identify your current Concourse version using 'concourse --version' or checking your deployment manifests
  2. Determine which version branch you're on (6.3.x or 6.4.x) to select the appropriate upgrade path
  3. For installations using Docker/docker-compose: Update the 'concourse/concourse' image tag to '6.3.1' or '6.4.1' in your docker-compose.yml and run 'docker-compose pull' followed by 'docker-compose up -d'
  4. For Kubernetes deployments using Helm: Update the 'image' or 'version' value in your Helm values file to '6.3.1' or '6.4.1', then run 'helm upgrade'
  5. For binary installations: Download the appropriate release from https://github.com/concourse/concourse/releases/tag/v6.3.1 or v6.4.1, replace the concourse binary, and restart the concourse worker and web services
  6. After upgrade, verify the GitLab auth connector is functioning correctly and test that user identity is properly validated
  7. If using GitLab user authentication (not groups), consider migrating affected users to GitLab groups configured in Concourse teams as mentioned in the advisory
Caveat Review release notes for 6.3.1 and 6.4.1 for any breaking changes between your current version and the target version before upgrading

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

Fix this in Concourse Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
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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-2020-5415 in production — separate from our analysis above.

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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