CVE intelligence and bounded remediation

CVE-2022-31108 — Mermaid Project Mermaid security vulnerability

Medium CVSS 6.1

Mermaid is a JavaScript based diagramming and charting tool that uses Markdown-inspired text definitions and a renderer to create and modify complex diagrams. An attacker is able to inject arbitrary `CSS` into the generated graph allowing them to change the styling of elements outside of the generated graph, and potentially exfiltrate sensitive information by using specially crafted `CSS` selectors. The following example shows how an attacker can exfiltrate the contents of an input field by bruteforcing the `value` attribute one character at a time. Whenever there is an actual match, an `http` request will be made by the browser in order to "load" a background image that will let an attacker know what's the value of the character. This issue may lead to `Information Disclosure` via CSS selectors and functions able to generate HTTP requests. This also allows an attacker to change the document in ways which may lead a user to perform unintended actions, such as clicking on a link, etc. This issue has been resolved in version 9.1.3. Users are advised to upgrade. Users unable to upgrade should ensure that user input is adequately escaped before embedding it in CSS blocks.

Severity
Medium
CVSS
6.1 (3.1)
Published
2022-06-28
CISA KEV
Not currently listed
Ecosystem
javascript/npm
Weaknesses
CWE-74, CWE-79

Affected products

  • mermaid_project / mermaid

Matched remediation archetype

Cross-site scripting and unsafe browser output

This catalog composition supplies bounded fallback guidance. Explicitly reviewed curated workflows load with the complete record below.

Check exposure

  • Trace reflected, stored, and DOM-derived untrusted values into HTML, attributes, URLs, styles, scripts, and client-side template sinks.
  • Identify affected origins, authenticated user roles, sensitive browser capabilities, and where content is shared across tenants.
  • Review framework escaping, rich-text sanitization, legacy templates, and client-side rendering paths.

Remediate safely

  • Use context-aware framework output encoding and safe DOM APIs; keep untrusted data out of executable contexts.
  • Sanitize intentionally supported markup with a maintained allowlist policy and validate URLs and attributes separately.
  • Update affected rendering components and add tests for every output context using inert sentinel markup.

Authoritative sources

Complete CVE record and remediation plan

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