Arbitrary Code Injection Affecting mermaid package, versions <10.9.6>=11.0.0-alpha.1 <11.15.0
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Start learning- Snyk IDSNYK-JS-MERMAID-16642055
- published12 May 2026
- disclosed11 May 2026
- creditzsxsoft
Introduced: 11 May 2026
CVE-2026-41159 (opens in a new tab)How to fix?
Upgrade mermaid to version 10.9.6, 11.15.0 or higher.
Overview
mermaid is a package for generation of diagrams and flowcharts from text in a similar manner as markdown.
Affected versions of this package are vulnerable to Arbitrary Code Injection due to improper sanitization of configuration options such as fontFamily, themeCSS, and altFontFamily. An attacker can inject arbitrary CSS that escapes diagram scoping and affects the entire page, potentially leading to page defacement or exfiltration of DOM attributes by crafting malicious configuration values.
Workaround
This vulnerability can be mitigated by setting the secure configuration value or by configuring securityLevel to sandbox.
PoC
%%{init: {"fontFamily": "x;a{b} :not(&){background:green !important} c{d}"}}%%
flowchart LR
A --> B