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GitLabApplication

CVE-2021-39908

HIGH · 7.5 CVSS v3.1 Published 2022-04-01
Fix available
A fix is available. Upgrade to 14.2.6 / 14.3.4 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges 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
In all versions of GitLab CE/EE starting from 0.8.0 before 14.2.6, all versions starting from 14.3 before 14.3.4, and all versions starting from 14.4 before 14.4.1 certain Unicode characters can be abused to commit malicious code into projects without being noticed in merge request or source code viewer UI.

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 Unicode character injection vulnerability in GitLab's merge request and source code viewer UI allows attackers to commit malicious code that appears innocuous or benign in the web interface, bypassing code review. The UI fails to properly render or display certain Unicode characters, hiding the actual code content from reviewers.

MitigationUpgrade GitLab to version 14.2.6, 14.3.4, 14.4.1 or later. Alternatively, perform code review directly from the command line rather than the web UI as a temporary compensating control.

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:>= 0.8.0, < 14.2.6>= 14.3.0, < 14.3.4= 14.4.0

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

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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. Determine installed GitLab version
    Run 'gitlab-rake gitlab:env:info' or check the Admin area under Settings > Metrics and profiling > GitLab configuration. Alternatively, check /opt/gitlab/version on the GitLab server.
    Affected if The installed version falls within: >= 0.8.0 and < 14.2.6, OR >= 14.3.0 and < 14.3.4, OR equals exactly 14.4.0
  2. Confirm web UI code review usage
    Identify if your team reviews merge requests and source code primarily through the GitLab web interface rather than cloning repositories and reviewing locally via command line.
    Affected if Code review is performed through the GitLab web UI (merge request diffs, file viewer) and the installed version is vulnerable
  3. Inspect recent merge request diffs for Unicode anomalies
    Use the GitLab API (GET /projects/:id/merge_requests/:iid/diffs) or manually review recent merged merge requests. Look for code that renders differently in the web UI than what git diff shows locally.
    Affected if Merge requests contain homograph attacks or invisible Unicode characters (zero-width characters, RTL override characters, combining characters) that are hidden or altered in the web UI display

You are affected if your GitLab version is within the vulnerable ranges AND you use the web UI to review merge requests or source code, allowing potentially malicious code to be hidden from review.

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 14.2.6 / 14.3.4 or later
Fixed in 14.2.614.3.4
Interim mitigation

Upgrade GitLab to version 14.2.6, 14.3.4, 14.4.1 or later. Alternatively, perform code review directly from the command line rather than the web UI as a temporary compensating control.

Recommended fix High confidence

Upgrade to GitLab 14.2.6, 14.3.4, or 14.4.1 (or later stable release) - choose based on your current version branch

  1. 1. Backup your GitLab instance database and configuration before upgrading.
  2. 2. Stop GitLab services (gitlab-ctl stop).
  3. 3. Update your package manager and install the latest GitLab version using your package manager (e.g., apt-get update && apt-get install gitlab-ce for Debian/Ubuntu, or yum install for RHEL/CentOS).
  4. 4. Alternatively, if using Docker, pull and run the fixed version: docker run -d gitlab/gitlab-ce:14.4.1 or a later stable version.
  5. 5. Reconfigure GitLab after upgrade: gitlab-ctl reconfigure.
  6. 6. Verify the upgrade was successful by checking the GitLab version in the Admin Area > Settings > General.
  7. 7. Test that Unicode characters are now properly displayed/rendered in the merge request and source code viewer UI to confirm the vulnerability is mitigated.
Caveat Review GitLab release notes for upgrade path; major version jumps may require intermediate upgrades; ensure compatibility with your underlying OS and dependencies

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
16.0 hours of engineering $2,840
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,544.

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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-2021-39908 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