CVE-2026-41159Public exploitNetwork attack vector

Page defacement and exfiltration via CSS scope escape

Published May 29, 2026 · Updated May 29, 2026

CSS injection in Mermaid before 10.9.6 and 11.0.0-alpha.1 through 11.14.0 allows remote attackers to alter host pages. The CSS namespace builder passes attacker-controlled fontFamily, themeCSS, or altFontFamily selectors to stylis, whose :not(&) handling omits the diagram ID prefix and hoists global at-rules. Exploitation requires an application to render attacker-controlled diagram configuration in a user-viewed page; injected rules can deface the page or exfiltrate DOM attributes, but do not execute JavaScript.

CVSS severity5.3
Medium
EPSS probability0.49%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

CSS injection in Mermaid before 10.9.6 and 11.0.0-alpha.1 through 11.14.0 allows remote attackers to alter host pages. The CSS namespace builder passes attacker-controlled fontFamily, themeCSS, or altFontFamily selectors to stylis, whose :not(&) handling omits the diagram ID prefix and hoists global at-rules. Exploitation requires an application to render attacker-controlled diagram configuration in a user-viewed page; injected rules can deface the page or exfiltrate DOM attributes, but do not execute JavaScript.

The record

CVE
CVE-2026-41159
Published
May 29, 2026
Updated
May 29, 2026
Vendor
Mermaid
Product
Mermaid
Classifications
CWE-94
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 29, 2026CVE publishedPublication date reported by the CVE source.
  2. May 29, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 10.9.6
  2. Affected versionversion=>= 11.0.0-alpha.1, < 11.15.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mermaid · Mermaidversion=< 10.9.6; version=>= 11.0.0-alpha.1, < 11.15.0

Published CVSS scores

5.3GitHubCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:L/SI:L/SA:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-94Improper Control of Generation of Code ('Code Injection')

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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