CVE-2026-41148

Description

Mermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams and charts. Versions 10.9.5 and prior, in addition to 11.0.0-alpha.1 through 11.12.0 are vulnerable to CSS injection through improper sanitization. The state diagram (and any other diagram type that routes user-controlled style strings through the createCssStyles parser) captures classDef values using an unrestricted regex that matches everything up to a newline. That value then flows unsanitized through addStyleClass() into createCssStyles() and is assigned to style.innerHTML, so a closing brace (}) in the value terminates the generated CSS selector and turns everything after it into a new CSS rule on the page. This enables page defacement, user tracking via url() callbacks, and DOM attribute exfiltration. This issue has been fixed in versions 10.9.6 and 11.15.0. If developers are unable to immediately upgrade, they can work around this issue by setting "securityLevel": "sandbox", which prevents the issue by rendering the mermaid diagram in a sandboxed <iframe>.

Overview

State: PUBLISHED
Assigner (CNA): GitHub_M
CVSS severity: MEDIUM
CVSS score: 5.3 / 10
CVSS vector: 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
Effective score: 5.3 / 10 MEDIUM source: CNA overview
CWE(s): CWE-94
Reserved: 2026-04-17
Published: 2026-05-22 22:03 UTC
Last updated: 2026-05-22 22:03 UTC
Source: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/41xxx/CVE-2026-41148.json
Linked Threat: CVE-2026-41148 — CVE-2026-41148

NVD triage scoring NVD CVE 2.0

Layer NVD adds on top of the CNA's CVE record — published / last-modified timestamps, exploitability / impact subscores, and the FIRST.org EPSS probability that this CVE will be exploited in the wild in the next 30 days.

EPSS score: 0.0006 (probability of exploitation in next 30 days)
EPSS percentile: 17.60% vs all CVEs — higher = more likely to be exploited, as of 2026-05-24

European Union Vulnerability Database ENISA EUVD

ENISA's official EU repository for curated vulnerability intelligence. Carries a separate identifier (EUVD-YYYY-NNNN) and frequently exposes an earlier-published description + CVSS than NVD does.

EUVD ID: EUVD-2026-31515
Assigner: GitHub_M
Published: May 22, 2026, 10:03:50 PM
Updated: May 27, 2026, 1:25:35 PM
EUVD base score (CVSS 4.0): 5.3 / 10
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
EUVD-reported EPSS: 0.0700
Vendors: mermaid-js
Products: mermaid (11.0.0-alpha.1, < 11.15.0)

mermaid (< 10.9.6)
Aliases: GHSA-xcj9-5m2h-648r

ENISA description: Mermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams and charts. Versions 10.9.5 and prior, in addition to 11.0.0-alpha.1 through 11.12.0 are vulnerable to CSS injection through improper sanitization. The state diagram (and any other diagram type that routes user-controlled style strings through the createCssStyles parser) captures classDef values using an unrestricted regex that matches everything up to a newline. That value then flows unsanitized through addStyleClass() into createCssStyles() and is assigned to style.innerHTML, so a closing brace (}) in the value terminates the generated CSS selector and turns everything after it into a new CSS rule on the page. This enables page defacement, user tracking via url() callbacks, and DOM attribute exfiltration. This issue has been fixed in versions 10.9.6 and 11.15.0. If developers are unable to immediately upgrade, they can work around this issue by setting "securityLevel": "sandbox", which prevents the issue by rendering the mermaid diagram in a sandboxed <iframe>.

EUVD references (6)

Affected products (1)

Vendor	Product	Versions	Platforms
mermaid-js	mermaid	`>= 11.0.0-alpha.1, < 11.15.0` (affected), `< 10.9.6` (affected)	—

Vendor references (6)

References embedded in the original CVE record by the assigning CNA.

https://github.com/mermaid-js/mermaid/security/advisories/GHSA-xcj9-5m2h-648r x_refsource_CONFIRM
https://github.com/mermaid-js/mermaid/commit/8fead23c59166b7bab6a39eac81acebee2859102 x_refsource_MISC
https://github.com/mermaid-js/mermaid/commit/e9b0f34d8d82a6260077764ee45e1d7d90957a0f x_refsource_MISC
https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.15.0 x_refsource_MISC
https://github.com/mermaid-js/mermaid/releases/tag/v10.9.6 x_refsource_MISC
https://mermaid.js.org/config/schema-docs/config.html#securitylevel x_refsource_MISC

MITRE references (1) cveawg.mitre.org

Pulled from MITRE's CVE Services API by the 🛰 Backfill from MITRE button.

https://mermaid.js.org/config/schema-docs/config.html#securitylevel x_refsource_MISC

Web references (8)

DuckDuckGo results ranked by threat-intel / vendor advisory domains. Generated by the 🔎 Find references (web) button above — same flow as the Remediations search.

https://github.com/mermaid-js/mermaid/commit/e9b0f34d8d82a6260077764ee45e1d7d90957a0f tenable:github.com
https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.15.0 tenable:github.com
https://github.com/mermaid-js/mermaid/releases/tag/v10.9.6 tenable:github.com
https://github.com/mermaid-js/mermaid/security/advisories/GHSA-xcj9-5m2h-648r tenable:github.com
https://www.first.org/epss/ tenable:www.first.org
https://github.com/mermaid-js/mermaid/commit/8fead23c59166b7bab6a39eac81acebee2859102 tenable:github.com
https://www.cve.org/CVERecord?id=CVE-2026-41148 tenable:www.cve.org
https://nvd.nist.gov/vuln/detail/CVE-2026-41148 tenable:nvd.nist.gov

Remediations (10)

Remediations are stored against the linked Threat row; the list below is deduplicated across both pages.

Windows Kerberos RC4 deprecation: what will break in Active ... - 4sysops

web:4sysops.com

Starting in April 2026 , Windows updates will change the default Kerberos ticket issuance behavior to AES-SHA1 for accounts without explicit encryption settings, while RC4 can still be used where explicitly enabled. This change, driven by CVE - 2026 -20833, affects every Windows Server environment where service accounts or devices still rely on RC4. Any service account, NAS device, or legacy ...

2026-05-26 02:50 UTC
CVE-2026-41148 - Vulnerability Details - OpenCVE

web:app.opencve.io

Mermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams and charts. Versions 10.9.5 and prior, in addition to 11.0.0-alpha.1 through 11.12. are vulnerable to CSS injection through improper sanitization. The state diagram (and any other diagram type that routes user-controlled style strings through the createCssStyles parser) captures classDef values using ...

2026-05-26 02:50 UTC
Security Advisory Bulletin 064 | Ubiquiti Community

web:community.ui.com

Published: May 21, 2026 Updated: May 22, 2026 Version: 1.1 Revision: 1.1 Summary 1 of 5 A malicious actor with access to the network and high privileges could exploit an Improper Input Validation vulnerability found in UniFi OS devices to execute a Command Injection. Affected Products: UniFi OS Server (Version 5.0.6 and earlier) Mitigation : Update your UniFi OS Server to Version 5.0.8 or later ...

2026-05-26 02:50 UTC
CISA Warns of Exploited Microsoft Defender 0-Day Flaws

web:cyberpress.org

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has added two actively exploited Microsoft Defender vulnerabilities to its Known Exploited Vulnerabilities (KEV) catalog, issuing an urgent remediation directive for federal agencies with a due date of June 3, 2026 .

2026-05-26 02:50 UTC
Microsoft Patch Tuesday March 2026 - 78 Vulnerabilities Fixed ...

web:cybersecuritynews.com

Microsoft released its March 2026 Patch Tuesday security update on March 10, 2026 , addressing 78 vulnerabilities across Windows, Microsoft Office, Azure, SQL Server, and .NET. The update includes one actively exploited zero-day vulnerability and multiple Critical-rated flaws demanding immediate attention from security teams. The most urgent fix this month is CVE - 2026 -21262, the sole zero-day ...

2026-05-26 02:50 UTC
Improper Control of Generation of Code ('Code Injection')

web:devhub.checkmarx.com

CWE-94 - Code Injection Code injection is a type of vulnerability that allows an attacker to execute arbitrary code. This vulnerability fully compromises the machine and can cause a wide variety of security issues, such as unauthorized access to sensitive information, manipulation of data, denial of service attacks etc. Code injection is different from command injection in the fact that it is ...

2026-05-26 02:50 UTC
Security Update Guide - Loading - Microsoft

web:msrc.microsoft.com

Security Updates Acknowledgements

2026-05-26 02:50 UTC
Oracle Critical Patch Update Advisory - April 2026

web:www.oracle.com

This Critical Patch Update contains 481 new security patches across the product families listed below. Please note that an MOS note summarizing the content of this Critical Patch Update and other Oracle Software Security Assurance activities is located at April 2026 Critical Patch Update: Executive Summary and Analysis.

2026-05-26 02:50 UTC
Windows 11 April 2026 Update tested: What's new, improved and fixed

web:www.windowslatest.com

Windows 11 April 2026 update adds Narrator Copilot support, faster Settings, File Explorer fixes, and key security improvements.

2026-05-26 02:50 UTC
Patch Tuesday May 2026: Security Updates & CVE Analysis

web:zecurit.com

Get the complete breakdown of Microsoft's May 2026 Patch Tuesday. We analyze the latest security updates and all critical CVEs .

2026-05-26 02:50 UTC

AI Forensic Analysis

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Raw JSON

The full cvelistV5 record. Download as CVE-2026-41148.json.

{
  "containers": {
    "cna": {
      "affected": [
        {
          "product": "mermaid",
          "vendor": "mermaid-js",
          "versions": [
            {
              "status": "affected",
              "version": ">= 11.0.0-alpha.1, < 11.15.0"
            },
            {
              "status": "affected",
              "version": "< 10.9.6"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Mermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams and charts. Versions 10.9.5 and prior, in addition to 11.0.0-alpha.1 through 11.12.0 are vulnerable to CSS injection through improper sanitization. The state diagram (and any other diagram type that routes user-controlled style strings through the createCssStyles parser) captures classDef values using an unrestricted regex that matches everything up to a newline. That value then flows unsanitized through addStyleClass() into createCssStyles() and is assigned to style.innerHTML, so a closing brace (}) in the value terminates the generated CSS selector and turns everything after it into a new CSS rule on the page. This enables page defacement, user tracking via url() callbacks, and DOM attribute exfiltration. This issue has been fixed in versions 10.9.6 and 11.15.0. If developers are unable to immediately upgrade, they can work around this issue by setting \"securityLevel\": \"sandbox\", which prevents the issue by rendering the mermaid diagram in a sandboxed <iframe>."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "LOW",
            "subConfidentialityImpact": "LOW",
            "subIntegrityImpact": "LOW",
            "userInteraction": "PASSIVE",
            "vectorString": "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",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "LOW"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-94",
              "description": "CWE-94: Improper Control of Generation of Code ('Code Injection')",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-22T22:03:50.872Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/mermaid-js/mermaid/security/advisories/GHSA-xcj9-5m2h-648r",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/mermaid-js/mermaid/security/advisories/GHSA-xcj9-5m2h-648r"
        },
        {
          "name": "https://github.com/mermaid-js/mermaid/commit/8fead23c59166b7bab6a39eac81acebee2859102",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/mermaid-js/mermaid/commit/8fead23c59166b7bab6a39eac81acebee2859102"
        },
        {
          "name": "https://github.com/mermaid-js/mermaid/commit/e9b0f34d8d82a6260077764ee45e1d7d90957a0f",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/mermaid-js/mermaid/commit/e9b0f34d8d82a6260077764ee45e1d7d90957a0f"
        },
        {
          "name": "https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.15.0",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.15.0"
        },
        {
          "name": "https://github.com/mermaid-js/mermaid/releases/tag/v10.9.6",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/mermaid-js/mermaid/releases/tag/v10.9.6"
        },
        {
          "name": "https://mermaid.js.org/config/schema-docs/config.html#securitylevel",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://mermaid.js.org/config/schema-docs/config.html#securitylevel"
        }
      ],
      "source": {
        "advisory": "GHSA-xcj9-5m2h-648r",
        "discovery": "UNKNOWN"
      },
      "title": "Mermaid: Improper sanitization of `classDefs` in diagrams leads to CSS injection"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-41148",
    "datePublished": "2026-05-22T22:03:50.872Z",
    "dateReserved": "2026-04-17T12:59:15.739Z",
    "dateUpdated": "2026-05-22T22:03:50.872Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}