TI-2026-29785 Aliases CVE-2026-41159 GHSA-87f9-hvmw-gh4p

Mermaid: Improper sanitization of configuration leads to CSS injection

LOW 25CWE-94Published 2026-05-29 · Updated 2026-07-01

Key facts

Attack vector: Network
Privileges required: None
User interaction: Passive
Attack complexity: Low
Attack requirements: None
Impact type: Code execution
Confidentiality · integrity · availability: None · Low · None
Fix status: Partial Red Hat: 3 without a fix

Attack profile from CVSS 4.0 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-94.

Summary

Mermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams and charts. Prior to 10.9.6 and 11.15.0, Mermaid's default configuration allows injecting CSS that applies outside of the Mermaid diagram via the fontFamily, themeCSS, and altFontFamily configuration options. The injected CSS exploits stylis's & (scope reference) handling. :not(&) escapes the #mermaid-xxx automatic scoping, applying styles to all page elements. Global at-rules (@font-face, @keyframes, @counter-style) are also injectable as stylis hoists them to top level. This allows page defacement and DOM attribute exfiltration via CSS :has() selectors. This vulnerability is fixed in 10.9.6 and 11.15.0.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00486 42nd percentileScored 2026-11-07

Fix Partial mermaid (mermaid-js): 11.15.0, 10.9.6mermaid (npm): 11.15.0, 10.9.6Red Hat: 3 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
mermaid-js	mermaid	11.0.0-alpha.1 to before 11.15.0; before 10.9.6	11.15.0, 10.9.6	Patch available	CNA
—	mermaid (npm)	11.0.0-alpha.1 to before 11.15.0	11.15.0	Patch available	GHSA-87f9-hvmw-gh4p
—	mermaid (npm)	before 10.9.6	10.9.6	Patch available	GHSA-87f9-hvmw-gh4p

mermaid Vendormermaid-js Affected 11.0.0-alpha.1 to before 11.15.0; before 10.9.6 Fixed in 11.15.0, 10.9.6 Patch available CNA
mermaid (npm) Vendor— Affected 11.0.0-alpha.1 to before 11.15.0 Fixed in 11.15.0 Patch available GHSA-87f9-hvmw-gh4p
mermaid (npm) Vendor— Affected before 10.9.6 Fixed in 10.9.6 Patch available GHSA-87f9-hvmw-gh4p

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:mermaid_project:mermaid::::::node.js::*	before 10.9.6; 11.0.0 to before 11.15.0	Vulnerable	mermaid-js

cpe:2.3:a:mermaid_project:mermaid:*:*:*:*:*:node.js:*:* Versions before 10.9.6; 11.0.0 to before 11.15.0 Vulnerable ·mermaid-js

Remediation

Fix · CNA mermaid (mermaid-js) Fixed in 11.15.0, 10.9.6
Fix · GHSA-87f9-hvmw-gh4p mermaid (npm) Fixed in 11.15.0 Advisory →
Fix · GHSA-87f9-hvmw-gh4p mermaid (npm) Fixed in 10.9.6 Advisory →

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

Product	Status	Plan or fix
Red Hat Build of Podman Desktop	Affected	No fix yet: Fix deferred
Red Hat OpenShift AI (RHOAI)	Affected	No fix yet: Fix deferred
Red Hat OpenShift Dev Spaces	Affected	No fix yet: Fix deferred

Timeline

2026-10-02 Threatist record created from CVE-2026-41159
2026-10-03 Alias added: GHSA-87f9-hvmw-gh4p

References

Advisory 2

Other 6

TI-2026-29778 Mermaid Gantt Charts are vulnerable to an Infinite Loop DoS CVSS 4.0MEDIUM 5.3
TI-2022-13152 Arbitrary `CSS` injection into the generated graph affecting the container HTML in mermaid.js CVSS 3.1MEDIUM 6.1
TI-2025-34614 Mermaid does not properly sanitize architecture diagram iconText leading to XSS CVSS 4.0MEDIUM 5.1
TI-2021-19667 Incorrect sanitisation function leads to `XSS` CVSS 3.1HIGH 7.2
TI-2021-14247 Mermaid before 8.11.0 allows XSS when the antiscript feature is used. CVSS 3.1MEDIUM 6.1

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences