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GitLabApplication

CVE-2023-3909

MEDIUM · 6.5 CVSS v3.1 Published 2023-11-06
Fix available
A fix is available. Upgrade to 16.3.6 / 16.4.2 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 12.3 before 16.3.6, all versions starting from 16.4 before 16.4.2, all versions starting from 16.5 before 16.5.1. A Regular Expression Denial of Service was possible by adding a large string in timeout input in gitlab-ci.yml file.

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 Denial of Service (ReDoS) vulnerability exists in GitLab CE/EE where parsing large strings in the timeout input field of .gitlab-ci.yml files can cause excessive CPU consumption due to inefficient regex processing, leading to service degradation or unavailability.

MitigationUpgrade GitLab to version 16.3.6, 16.4.2, 16.5.1 or later. Alternatively, restrict who can modify CI/CD pipeline configurations and validate .gitlab-ci.yml files before acceptance.

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:>= 12.3.0, < 16.3.6>= 16.4.0, < 16.4.2= 16.5.0

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 the installed GitLab version
    Run `sudo gitlab-rake gitlab:env:info` or check the GitLab admin panel under Help > Version. Alternatively, check the /opt/gitlab/version file.
    Affected if The installed version is 12.3.0 or later but below 16.3.6, OR 16.4.0 or later but below 16.4.2, OR exactly 16.5.0.
  2. Verify CI/CD pipeline functionality is enabled
    Check if projects have access to CI/CD settings by navigating to a project Settings > CI/CD > General pipelines, or query the GitLab API: `curl -s "https://gitlab.example.com/api/v4/version"`.
    Affected if CI/CD pipelines are active and users can create or modify .gitlab-ci.yml files.
  3. Confirm if untrusted users can modify CI/CD configurations
    Review the group/project member roles and CI/CD settings. Check if external users, public project contributors, or users without maintainer privileges can push .gitlab-ci.yml files to repositories.
    Affected if Users with developer, maintainer, or push access to repositories can modify CI/CD configuration files.
  4. Inspect .gitlab-ci.yml files for timeout field usage
    Search repositories for .gitlab-ci.yml files containing the `timeout` keyword, especially where timeout values may contain unusually long strings. Use GitLab API or repository search: `grep -r "timeout:" */*.yml`.
    Affected if The instance hosts repositories with .gitlab-ci.yml files that contain timeout fields accessible to users who can trigger pipeline parsing.

You are affected if your GitLab version falls within the vulnerable ranges AND CI/CD pipelines are enabled with any user ability to modify .gitlab-ci.yml files.

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 16.3.6 / 16.4.2 or later
Fixed in 16.3.616.4.2
Interim mitigation

Upgrade GitLab to version 16.3.6, 16.4.2, 16.5.1 or later. Alternatively, restrict who can modify CI/CD pipeline configurations and validate .gitlab-ci.yml files before acceptance.

Recommended fix High confidence

16.5.1 (or 16.3.6 / 16.4.2 for respective version branches)

  1. Back up your GitLab instance database and repositories
  2. Schedule a maintenance window for the upgrade (GitLab upgrades require downtime)
  3. For GitLab installations using package manager (Omnibus): Stop GitLab services with 'gitlab-ctl stop'
  4. Upgrade GitLab to version 16.3.6 (if currently on 12.3.0 through 16.3.x), version 16.4.2 (if currently on 16.4.0-16.4.1), or version 16.5.1 (if currently on 16.5.0)
  5. For package manager installations, run 'gitlab-ctl restart' after upgrade completes
  6. Verify GitLab is running and accessible
  7. Confirm the version upgrade was successful by checking Help > Version information
Caveat GitLab upgrades may require database migrations; ensure adequate downtime and test in staging first. Review GitLab release notes for version-specific breaking changes between your current version and target 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
  • Implementation4.0 h
  • Testing8.0 h
  • Review / QA4.0 h
18.0 hours of engineering $3,040
Get the upgrade done

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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-2023-3909 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