CVE-2020-5415
Concourse's GitLab auth allows impersonation
CVE-2020-5415 is a critical vulnerability (CVSS 10.0) in Pivotal Software Concourse, published August 12, 2020. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.22%, the 69th percentile. Fixed in github.com/concourse/concourse 6.4.1.
- Severity
- 10.0 CriticalCVSS 3.0, CVE List
- Exploit chance
- 1.22%EPSS, 69th percentile
- Exploitation
- None knownNot on CISA’s or ENISA’s lists
- Fixed in
6.4.1github.com/concourse/concourse +11 more
Description
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- Low
Exploit likelihood
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
github.com/concourse/concourseGo | 6.4.0 to 6.4.0 | 6.4.1 |
github.com/concourse/dexGo | 6.4.0 to 6.4.0 | 6.4.1 |
github.com/concourse/dexGo | before 0.0.0-20200730150203-821b48abfd88 | 0.0.0-20200730150203-821b48abfd88 |
github.com/concourse/concourseGo | before 0.0.0-20200730151558-b00d1c8d8576 | 0.0.0-20200730151558-b00d1c8d8576 |
github.com/concourse/concourseGo | 1.6.1 to 6.3.0 | 6.3.1 |
github.com/concourse/dexGo | 0.0.0 up to 6.3.0 | 6.3.0 |
github.com/concourse/concourseGo | 0.0.0 up to 1.6.1-0.20200730151558-b00d1c8d8576 | 1.6.1-0.20200730151558-b00d1c8d8576 |
concourseBitnami | before 6.3.1, 6.4.0 up to 6.4.1 | 6.3.16.4.1 |
github.com/concourse/concourseGo | 6.4.0 up to 6.4.1 | 6.4.1 |
github.com/concourse/concourseGo | 1.6.1 up to 6.3.1 | 6.3.1 |
github.com/concourse/dexGo | 6.4.0 up to 6.4.1 | 6.4.1 |
github.com/concourse/dexGo | 0.0.0 up to 6.3.1 | 6.3.1 |
What each source reports
CVE List Score used
Concourse's GitLab auth allows impersonation
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.
- Record
CVE-2020-5415- CVSS 3.0
- 10.0 Critical
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:L - Weakness
- CWE-290
- Updated
- 2026-11-02
EUVDEUVD-2021-2453
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.
- Record
EUVD-2021-2453- CVSS 3.0
- 10.0 Critical
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:L - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-627p-rr78-99rj
GitLab auth uses full name instead of username as user ID, allowing impersonation
Impact
Installations which use the GitLab auth connector are vulnerable to identity spoofing by way of configuring a GitLab account with the same full name as another GitLab user who is granted access to a Concourse team by having their full name listed under users in the team configuration or given to the --gitlab-user flag.
See the GitLab auth docs for details.
Concourse installations which do not configure the GitLab auth connector are not affected.
Patches
Concourse v6.3.1 and v6.4.1 were both released with a fix on August 4th, 2020.
Both versions change the GitLab connector to use the username, rather than the full name. This was always the intent, and the previous behavior was originally reported as a bug (concourse/dex#7) prior to being reported as a security issue.
Any Concourse teams which configure GitLab users will have to switch each user from their full name to their username upon upgrading to these versions.
Workarounds
GitLab groups do not have this vulnerability, so GitLab users may be moved into groups which are then configured in the Concourse team.
References
- concourse/dex#12: PR with the fix
For more information
If you have any questions or comments about this advisory, you may reach us privately at concourseteam+security@gmail.com.
- Record
GHSA-627p-rr78-99rj- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - Weakness
- CWE-290
- Updated
- 2026-11-02
NVD
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.
- Record
CVE-2020-5415- CVSS 3.1
- 10.0 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N - CVSS 3.0
- 10.0 Critical
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:L - CVSS 2.0
- 6.4 Medium
AV:N/AC:L/Au:N/C:P/I:P/A:N - Weakness
- CWE-290
- Updated
- 2026-11-02
OSV
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.
- Record
CVE-2020-5415- CVSS 3.1
- 10.0 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N - Updated
- 2026-11-02
OSVGHSA-627p-rr78-99rj
GitLab auth uses full name instead of username as user ID, allowing impersonation
Impact
Installations which use the GitLab auth connector are vulnerable to identity spoofing by way of configuring a GitLab account with the same full name as another GitLab user who is granted access to a Concourse team by having their full name listed under users in the team configuration or given to the --gitlab-user flag.
See the GitLab auth docs for details.
Concourse installations which do not configure the GitLab auth connector are not affected.
Patches
Concourse v6.3.1 and v6.4.1 were both released with a fix on August 4th, 2020.
Both versions change the GitLab connector to use the username, rather than the full name. This was always the intent, and the previous behavior was originally reported as a bug (concourse/dex#7) prior to being reported as a security issue.
Any Concourse teams which configure GitLab users will have to switch each user from their full name to their username upon upgrading to these versions.
Workarounds
GitLab groups do not have this vulnerability, so GitLab users may be moved into groups which are then configured in the Concourse team.
References
- concourse/dex#12: PR with the fix
For more information
If you have any questions or comments about this advisory, you may reach us privately at concourseteam+security@gmail.com.
- Record
GHSA-627p-rr78-99rj- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - Weakness
- CWE-290
- Updated
- 2026-11-02
OSVBIT-concourse-2020-5415No score
Concourse's GitLab auth allows impersonation
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.
- Record
BIT-concourse-2020-5415- Updated
- 2026-11-02
History
| Recorded | Changed | Sources |
|---|---|---|
| facts | ||
| aliases, published | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.