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GitLabApplication

CVE-2026-5173

HIGH · 8.5 CVSS v3.1 Published 2026-04-08
Fix available
A fix is available. Upgrade to 18.8.9 / 18.9.5 or later.
See remediation →
91/100
Remediation priority · Urgent
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
GitLab has remediated an issue in GitLab CE/EE affecting all versions from 16.9.6 before 18.8.9, 18.9 before 18.9.5, and 18.10 before 18.10.3 that could have allowed an authenticated user to invoke unintended server-side methods through websocket connections due to improper access control.

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

GitLab CE/EE versions 16.9.6 through 18.10.2 contain an improper access control vulnerability in websocket handling that allows authenticated users to invoke unintended server-side methods through websocket connections.

MitigationUpgrade GitLab to version 18.8.9, 18.9.5, 18.10.3 or later. For systems that cannot immediately upgrade, restrict websocket access through network segmentation or review websocket endpoint configurations.

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:>= 16.9.6, < 18.8.9>= 18.9.0, < 18.9.5>= 18.10.0, < 18.10.3

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
Changed
Confidentiality
High
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N

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 `gitlab-rake gitlab:env:info` or check `/opt/gitlab/version` ( Omnibus installations) or look for the VERSION file in the GitLab installation directory (source installations)
    Affected if The displayed version falls within one of these ranges: >= 16.9.6 and < 18.8.9; >= 18.9.0 and < 18.9.5; >= 18.10.0 and < 18.10.3
  2. Confirm websocket support is enabled
    Check the GitLab configuration file (usually `/etc/gitlab/gitlab.rb` for Omnibus) for the `gitlab_rails['websocket_enable']` setting, or verify that web sockets are not explicitly disabled
    Affected if Websockets are enabled (the default state) - the vulnerability exists in the websocket connection handling code itself, not in a disabled feature
  3. Verify the instance accepts authenticated websocket connections
    Check if the GitLab instance has active user authentication and that ActionCable (websocket support for real-time features) is operational. This can be confirmed by logging into GitLab and checking if real-time features (such as live merge request updates, CI pipeline status, or Web IDE) function properly
    Affected if Authenticated users can establish websocket connections to the GitLab instance - the vulnerability allows authenticated users to invoke unintended server-side methods through these connections

You are affected if your GitLab version is 16.9.6 through 18.8.8, 18.9.0 through 18.9.4, or 18.10.0 through 18.10.2 and your instance has websocket connections enabled (the default) for authenticated users.

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 18.8.9 / 18.9.5 / 18.10.3 or later
Fixed in 18.8.918.9.518.10.3
Interim mitigation

Upgrade GitLab to version 18.8.9, 18.9.5, 18.10.3 or later. For systems that cannot immediately upgrade, restrict websocket access through network segmentation or review websocket endpoint configurations.

Recommended fix High confidence

18.10.3 (or 18.8.9 / 18.9.5 depending on your current branch)

  1. 1. Back up your GitLab instance data and configuration before starting the upgrade.
  2. 2. Review the GitLab upgrade documentation for your installation method (Omnibus, source, or Helm chart).
  3. 3. Ensure your system meets the requirements for the target version.
  4. 4. For Omnibus installations: Update your package repository and install the new version using 'gitlab-ctl restart' after upgrade.
  5. 5. For source installations: Stop GitLab services, fetch the new version from the repository, run database migrations with 'bundle exec rake db:migrate', and restart services.
  6. 6. Verify the upgrade was successful by checking the GitLab version in the Admin Area.
  7. 7. Confirm the vulnerability is resolved by testing WebSocket functionality.

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
  • Testing3.0 h
  • Review / QA2.0 h
15.0 hours of engineering $2,690
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,304.

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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-2026-5173 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