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GitLabApplication

CVE-2021-39887

MEDIUM · 5.4 CVSS v3.1 Published 2021-10-05
Fix available
A fix is available. Upgrade to 14.1.7 / 14.2.5 or later.
See remediation →
58/100
Remediation priority · Elevated
Remotely reachable

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
A stored Cross-Site Scripting vulnerability in the GitLab Flavored Markdown in GitLab CE/EE version 8.4 and above allowed an attacker to execute arbitrary JavaScript code on the victim's behalf.

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 stored Cross-Site Scripting (XSS) vulnerability in GitLab Flavored Markdown rendering in GitLab CE/EE versions 8.4 and above allows attackers to inject malicious JavaScript payloads into stored markdown content. When victims view the crafted markdown, the embedded script executes in their browser context.

MitigationUpgrade GitLab to the patched version released for this CVE. Until patched, restrict or sanitize user-submitted markdown content in affected GitLab instances.

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:>= 8.4.0, < 14.1.7>= 14.2, < 14.2.5>= 14.3, < 14.3.1

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
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/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
    Log into the GitLab admin panel and navigate to the Admin Area > Overview > Dashboard, or run `sudo gitlab-rake gitlab:env:info` from the command line
    Affected if The displayed version falls within these ranges: 8.4.0 to 14.1.6, 14.2.0 to 14.2.4, or 14.3.0
  2. Confirm the GitLab installation type
    Verify whether you are running GitLab Community Edition (CE) or Enterprise Edition (EE) - check the admin panel footer or run `sudo gitlab-rake gitlab:env:info`
    Affected if Running CE or EE versions 8.4.0 or later that are not patched to 14.1.7, 14.2.5, or 14.3.1 respectively
  3. Verify markdown rendering is active
    Confirm that GitLab Flavored Markdown rendering is enabled in the instance. Check Admin Area > Settings > Preferences > Markdown section, or inspect a sample issue, merge request, comment, or wiki page that contains markdown
    Affected if Markdown rendering is enabled (this is the default state in GitLab) and the instance accepts user-submitted content via issues, merge requests, comments, or wikis
  4. Assess user content submission exposure
    Review whether the GitLab instance allows submissions from authenticated or external users. Check project settings for issue tracking, merge request creation, comment capabilities, and wiki access. Query the database if you have direct access: `sudo gitlab-psql -d gitlabhq_production -c "SELECT COUNT(*) FROM notes WHERE note LIKE '%<script%' OR note LIKE '%javascript:%';"` for suspicious patterns in comments
    Affected if The instance accepts user-generated markdown content (issues, MRs, comments, wikis) and contains or has contained unsanitized markdown with potential XSS payloads

You are affected if your GitLab version is 8.4.0 or later but below 14.1.7, 14.2.5, or 14.3.1 AND the instance allows users to submit markdown content that gets rendered in the browser.

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 14.1.7 / 14.2.5 / 14.3.1 or later
Fixed in 14.1.714.2.514.3.1
Interim mitigation

Upgrade GitLab to the patched version released for this CVE. Until patched, restrict or sanitize user-submitted markdown content in affected GitLab instances.

Recommended fix High confidence

14.1.7 (or latest 14.x stable)

  1. 1. Backup your GitLab instance database and repository data before upgrading
  2. 2. Check your current GitLab version by navigating to Admin Area > Settings > General > GitLab configuration
  3. 3. Stop GitLab services using: sudo gitlab-ctl stop
  4. 4. Update to the appropriate fixed version based on your current branch: For 14.1.x branch, upgrade to 14.1.7 or later; For 14.2.x branch, upgrade to 14.2.5 or later; For 14.3.x branch, upgrade to 14.3.1 or later; For any other version, upgrade to the latest stable 14.x release
  5. 5. Update GitLab package: sudo apt-get update && sudo apt-get install gitlab-ce (or gitlab-ee)
  6. 6. Reconfigure GitLab: sudo gitlab-ctl reconfigure
  7. 7. Start GitLab services: sudo gitlab-ctl start
  8. 8. Verify the upgrade by checking Admin Area > Settings > General to confirm the new version is running
Caveat Major version upgrades (e.g., 14.x to 15.x) may require additional migration steps; review GitLab upgrade guides for skipping major versions

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
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.

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-2021-39887 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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