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GitLabApplication

CVE-2021-22242

MEDIUM · 5.4 CVSS v3.1 Published 2021-08-25
Fix available
A fix is available. Upgrade to 13.12.9 / 14.0.7 or later.
See remediation →
58/100
Remediation priority · Elevated
High EPSS 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
Insufficient input sanitization in Mermaid markdown in GitLab CE/EE version 11.4 and up allows an attacker to exploit a stored cross-site scripting vulnerability via a specially-crafted markdown

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 exists in GitLab CE/EE due to insufficient input sanitization of Mermaid markdown. Attackers can inject malicious JavaScript via specially-crafted markdown that gets rendered in the Mermaid diagram component, allowing script execution in the context of other users viewing the content.

MitigationUpgrade to the patched GitLab version or implement output encoding/sanitization specifically for Mermaid markdown rendering to strip malicious script payloads before display.

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:>= 11.4.0, < 13.12.9>= 14.0.0, < 14.0.7>= 14.1.0, < 14.1.2

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
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 GitLab version
    Access the GitLab admin area, check the /help page, or run 'gitlab-rake gitlab:env:info' to retrieve the installed version
    Affected if the installed version falls within any of these ranges: >= 11.4.0 and < 13.12.9, OR >= 14.0.0 and < 14.0.7, OR >= 14.1.0 and < 14.1.2
  2. Confirm Mermaid markdown rendering is enabled
    Verify that GitLab's markdown rendering supports Mermaid diagrams; check if users can create issues, merge requests, or wikis containing Mermaid code blocks (```mermaid)
    Affected if Mermaid diagram rendering is active and users can author or view markdown content with Mermaid blocks
  3. Inspect for malicious Mermaid content
    Search repositories, issues, merge requests, snippets, and wikis for Mermaid code blocks that may contain injected script tags or event handlers within the diagram definition
    Affected if any Mermaid content exists that contains script tags, javascript: URLs, or event handler attributes like onload, onerror, or onclick
  4. Verify output sanitization status
    If possible, check whether custom sanitization filters or web application firewall rules are applied specifically to Mermaid markdown rendering
    Affected if no additional sanitization is applied beyond GitLab's default rendering, and the version is in the affected range

A user is affected if their GitLab version falls within the vulnerable ranges and Mermaid markdown rendering is enabled, allowing stored XSS payloads injected via Mermaid diagrams to execute in other users' browsers.

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 13.12.9 / 14.0.7 / 14.1.2 or later
Fixed in 13.12.914.0.714.1.2
Interim mitigation

Upgrade to the patched GitLab version or implement output encoding/sanitization specifically for Mermaid markdown rendering to strip malicious script payloads before display.

Recommended fix High confidence

Upgrade to GitLab 13.12.9, 14.0.7, 14.1.2, or later (preferably latest stable release such as 14.x or 15.x)

  1. 1. Back up your GitLab instance data before proceeding with the upgrade
  2. 2. Plan your upgrade path based on your current version - ensure you upgrade to a patched version: 13.12.9+, 14.0.7+, 14.1.2+, or preferably the latest stable release
  3. 3. For GitLab installations using Omnibus: run 'sudo gitlab-ctl stop' to stop services, then upgrade using your package manager (e.g., 'sudo apt-get update && sudo apt-get install gitlab-ce' or 'sudo yum install gitlab-ce')
  4. 4. For source installations: follow the upgrade documentation at https://docs.gitlab.com/ee/update/ to compile the new version from source
  5. 5. After installation, run 'sudo gitlab-ctl reconfigure' to apply configuration
  6. 6. Verify the upgrade was successful by checking GitLab version with 'sudo gitlab-rake gitlab:env:info'
  7. 7. Test that Mermaid markdown rendering works correctly and the XSS vulnerability is no longer present
Caveat Review GitLab upgrade guidelines for any version-specific migration notes; major version jumps (e.g., 13.x to 14.x) may require additional migration steps

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

Fix this in GitLab Scoped from the published advisory
  • Consultation2.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,290
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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-2021-22242 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