How severe is CVE-2020-5415?

CVE-2020-5415 has a CVSS score of 10/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2020-5415?

CVE-2020-5415 affects the following packages: github.com/concourse/concourse (Go), github.com/concourse/concourse (Go), github.com/concourse/dex (Go), github.com/concourse/dex (Go), github.com/concourse/dex (Go), github.com/concourse/concourse (Go), github.com/concourse/concourse (Go). Ecosystems affected: Go.

How do I fix CVE-2020-5415?

Update github.com/concourse/concourse to 6.4.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-5415 is resolved across your whole dependency graph.

How do I detect CVE-2020-5415 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/concourse/concourse, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2020-5415 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2020-5415 actively exploited in the wild?

No public exploit code has been indexed for CVE-2020-5415 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2020-5415?

CVE-2020-5415 has an EPSS (Exploit Prediction Scoring System) score of 1.2%, placing it in the 69th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2020-5415?

CVE-2020-5415 is classified as CWE-290 (CWE-290). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2020-5415 published, and has it been updated?

CVE-2020-5415 was published on August 12, 2020 and was last updated on October 20, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹

🐹 Go

Not in CISA KEV

CRITICAL severity

CVE-2020-5415 — concourse

CRITICAL

CVE-2020-5415 is a critical-severity (CVSS 10) CWE-290 vulnerability in github.com/concourse/concourse. A fix is available for github.com/concourse/concourse — see the affected versions and patch details below.

GitLab auth uses full name instead of username as user ID, allowing impersonation

Also known asBIT-concourse-2020-5415GHSA-627p-rr78-99rj

Published

Aug 12, 2020

Updated

Oct 20, 2026

Affected

7 pkgs

Patched

7 / 7

Exploits

None indexed

Exploitation data as of Nov 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs69th percentile — riskier than 69% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

7 pkgs affected

🐹github.com/concourse/concourse🐹github.com/concourse/concourse🐹github.com/concourse/dex🐹github.com/concourse/dex🐹github.com/concourse/dex🐹github.com/concourse/concourse🐹github.com/concourse/concourse

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

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 [email protected].

Affected Packages

7 total 7 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/concourse/concourse`	≥ 6.4.0&&< 6.4.1	6.4.1`go get github.com/concourse/concourse@v6.4.1`
🐹Go	`github.com/concourse/concourse`	≥ 1.6.1&&< 6.3.1	6.3.1`go get github.com/concourse/concourse@v6.3.1`
🐹Go	`github.com/concourse/dex`	≥ 6.4.0&&< 6.4.1	6.4.1`go get github.com/concourse/dex@v6.4.1`
🐹Go	`github.com/concourse/dex`	≥ 0.0.0&&< 6.3.1	6.3.1`go get github.com/concourse/dex@v6.3.1`
🐹Go	`github.com/concourse/dex`	all versions	0.0.0-20200730150203-821b48abfd88`go get github.com/concourse/dex@v0.0.0-20200730150203-821b48abfd88`
🐹Go	`github.com/concourse/concourse`	all versions	0.0.0-20200730151558-b00d1c8d8576`go get github.com/concourse/concourse@v0.0.0-20200730151558-b00d1c8d8576`

Affected Products

1 product · 2 configurations

Application

concoursepivotal_software

≥ 6.4.0 && < 6.4.1

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/concourse/concourse, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/concourse/concourse to 6.4.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-5415 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### 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](https://concourse-ci.org/gitlab-auth.html) for details. Concourse installations which do not configure the GitLab auth connector are not affected. ### Patches Concourse [v6.3.1](https://github.com/concourse/concourse/releases/tag/v6