GitLabApplication
CVE-2021-39937
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 · uneditedA collision in access memoization logic in all versions of GitLab CE/EE before 14.3.6, all versions starting from 14.4 before 14.4.4, all versions starting from 14.5 before 14.5.2, leads to potential elevated privileges in groups and projects under rare circumstances
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 · moderate confidenceA collision vulnerability in GitLab's access memoization logic allows cached access control decisions to be incorrectly shared between different users or contexts, potentially enabling privilege escalation in groups and projects.
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
GitLabApplication
< 14.3.6>= 14.4.0, < 14.4.4>= 14.5.0, < 14.5.2CVSS 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
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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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Determine installed GitLab versionRun `gitlab-rake gitlab:env:info` or check the Admin UI under /admin/application_settings or inspect /opt/gitlab/versionAffected if Version falls outside the safe ranges: not 14.3.6+, 14.4.4+, or 14.5.2+
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Verify GitLab is running as a group or project instanceConfirm the GitLab instance hosts groups and projects with multiple users by checking for group/project namespaces via the UI or APIAffected if The instance hosts groups or projects where access control between different users or subgroups is relevant
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Identify if custom memoization extensions existInspect Ruby code in /opt/gitlab/embedded/service/gitlab-rails for custom access memoization implementations in models related to authorization (e.g., app/models/ability.rb, app/services/)Affected if Custom code overrides or extends the built-in access memoization logic, increasing the attack surface for collision exploits
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Check for unusual access patterns in audit logsReview GitLab audit logs (Admin Area > Monitoring > Audit Events) for anomalous access patterns where users may have received permissions from other user contextsAffected if Audit logs show unexpected access grants or permission inheritance between unrelated users or projects
You are affected if your GitLab version is below 14.3.6, below 14.4.4 (if using 14.4.x), or below 14.5.2 (if using 14.5.x or higher), and the instance hosts groups or projects with multiple users where access control matters.
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.
dbcve · scoped14.3.614.4.414.5.2
Upgrade GitLab to version 14.3.6, 14.4.4, 14.5.2 or later to remediate the access memoization collision that could allow privilege escalation.
14.3.6, 14.4.4, or 14.5.2 (minimum fixed versions for their respective branches)
- Back up your GitLab instance database and repositories before proceeding with the upgrade
- Stop GitLab services to prevent data inconsistency during upgrade
- Update your GitLab installation to version 14.3.6, 14.4.4, or 14.5.2 (whichever is appropriate for your branch)
- Run 'gitlab-ctl reconfigure' to apply configuration changes
- Run 'gitlab-rake db:migrate' to ensure database migrations are applied
- Restart GitLab services
- Verify the upgrade was successful by checking the GitLab version and testing user access controls
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in GitLab
Scoped from the published advisory
- Consultation4.0 h
- Implementation6.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,544.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-39937 — 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-2021-39937 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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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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