# Mermaid: Improper sanitization of configuration leads to CSS injection

Advisory record · `GHSA-87f9-hvmw-gh4p`

- **Identifiers:** `GHSA-87f9-hvmw-gh4p` · `CVE-2026-41159`
- **State:** Confirmed
- **Severity:** CVSS 5.3 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-94](https://cwe.mitre.org/data/definitions/94.html)
- **Tags:** [Code injection](https://agentprime.io/advisories/tag/code-injection.md)
- **Published:** 11 May 2026
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 11 May 2026, 19:37 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `mermaid` (npm): affected `>=11.0.0-alpha.1, <11.15.0 || <10.9.6`; fixed in `11.15.0`, `10.9.6`

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 5.3 Medium, CVSS 4.0: `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:L/SI:L/SA:L`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0049, the 42nd percentile, on 14 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

This record came from the full history of the GitHub Advisory Database, published 11 May 2026. New records show when each source confirmed them.

## Sources

- [GitHub Advisory Database: GHSA-87f9-hvmw-gh4p](https://github.com/advisories/GHSA-87f9-hvmw-gh4p)
- [OSV: GHSA-87f9-hvmw-gh4p](https://osv.dev/vulnerability/GHSA-87f9-hvmw-gh4p)
- <https://github.com/mermaid-js/mermaid/security/advisories/GHSA-87f9-hvmw-gh4p>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-41159>
- <https://github.com/mermaid-js/mermaid/commit/64769738d5b59211e1decb471ffbaca8afec51aa>
- <https://github.com/mermaid-js/mermaid/commit/a9d9f0d8eb790349121508688cd338253fd80d76>
- <https://github.com/mermaid-js/mermaid>
- <https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.15.0>
- <https://github.com/mermaid-js/mermaid/releases/tag/mermaid@11.15.0>
- <https://github.com/mermaid-js/mermaid/releases/tag/v10.9.6>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-87f9-hvmw-gh4p>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-87f9-hvmw-gh4p/>. Everything for agents: <https://agentprime.io/llms.txt>.