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GitLabApplication

CVE-2021-39917

MEDIUM · 6.5 CVSS v3.1 Published 2021-12-13
Fix available
A fix is available. Upgrade to 14.3.6 / 14.4.4 or later.
See remediation →
71/100
Remediation priority · Elevated
Remotely reachable Zero-click

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
An issue has been discovered in GitLab CE/EE affecting all versions starting from 12.9 before 14.3.6, all versions starting from 14.4 before 14.4.4, all versions starting from 14.5 before 14.5.2. A regular expression related to quick actions features was susceptible to catastrophic backtracking that could cause a DOS attack.

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

A regular expression in GitLab's quick actions feature suffers from catastrophic backtracking (ReDoS vulnerability), allowing attackers to cause denial of service by providing specially crafted input that triggers exponential regex processing time.

MitigationUpgrade to GitLab 14.3.6, 14.4.4, 14.5.2 or later versions to patch the vulnerable regex pattern in the quick actions component.

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
Affected:>= 12.9.0, < 14.3.6>= 14.4.0, < 14.4.4>= 14.5.0, < 14.5.2

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
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify GitLab installation version
    Access the GitLab Admin area and navigate to the 'Version' section, or run `gitlab-rake gitlab:env:info` on the server to retrieve the exact GitLab version number
    Affected if The displayed version falls within any of these ranges: 12.9.0 to 14.3.5, 14.4.0 to 14.4.3, or 14.5.0 to 14.5.1
  2. Confirm quick actions feature is accessible
    Verify that the quick actions feature is enabled. In GitLab, quick actions are available in issue/MR descriptions and comments. Check if regular users or external users can submit comments or descriptions where quick action syntax is processed
    Affected if The quick actions feature is accessible to users who can submit content (issues, merge requests, comments) and the GitLab version is in the affected ranges
  3. Compare installed version against CVE ranges
    Take the exact version number obtained in step 1 and compare it numerically against the three vulnerable ranges: 12.9.0 <= version < 14.3.6 OR 14.4.0 <= version < 14.4.4 OR 14.5.0 <= version < 14.5.2
    Affected if The version matches any of the three vulnerable version ranges listed in the CVE

You are affected if your GitLab version is 12.9.0 through 14.3.5, 14.4.0 through 14.4.3, or 14.5.0 through 14.5.1, and users can submit input to the quick actions feature.

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 14.3.6 / 14.4.4 / 14.5.2 or later
Fixed in 14.3.614.4.414.5.2
Interim mitigation

Upgrade to GitLab 14.3.6, 14.4.4, 14.5.2 or later versions to patch the vulnerable regex pattern in the quick actions component.

Recommended fix High confidence

14.3.6, 14.4.4, or 14.5.2 (or latest stable 14.6+)

  1. Create a complete backup of the GitLab instance including database and repositories
  2. Review the GitLab upgrade path documentation for your current version
  3. Upgrade to one of the fixed releases: 14.3.6, 14.4.4, or 14.5.2 (or the latest stable version 14.6.0 or later)
  4. Follow the standard GitLab upgrade procedure for your installation method (package, source, or Docker)
  5. After upgrade, verify the quick actions feature functions normally and monitor for any performance issues
Caveat Upgrading across multiple minor versions may require sequential upgrades; review GitLab upgrade path docs for your current version

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

Fix this in GitLab Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,060
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,696.

Scan for this in your stack

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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-2021-39917 in production — separate from our analysis above.

No notes yet

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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