How severe is CVE-2021-43861?

CVE-2021-43861 has a CVSS 3.x base score of 7.2, rated high severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-43861 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (56th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-43861?

CVE-2021-43861 affects Mermaid Project Mermaid. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-43861?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-43861 published?

CVE-2021-43861 was published on 2021-12-30 and last updated on 2026-06-17.

CVE-2021-43861

CVE-2021-43861 is a high-severity vulnerability in Mermaid Project Mermaid with a CVSS 3.x base score of 7.2. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-20.

Key facts

Severity: High (CVSS 3.x base score 7.2)
CVSS v2: 3.5
EPSS exploit prediction: 1% (56th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Mermaid Project Mermaid
Published: 2021-12-30
Last modified: 2026-06-17

Description

Mermaid is a Javascript based diagramming and charting tool that uses Markdown-inspired text definitions and a renderer to create and modify complex diagrams. Prior to version 8.13.8, malicious diagrams can run javascript code at diagram readers' machines. Users should upgrade to version 8.13.8 to receive a patch. There are no known workarounds aside from upgrading.

Frequently asked questions

What is CVE-2021-43861?: Mermaid is a Javascript based diagramming and charting tool that uses Markdown-inspired text definitions and a renderer to create and modify complex diagrams. Prior to version 8.13.8, malicious diagrams can run javascript code at diagram readers' machines. Users should upgrade to version 8.13.8 to receive a patch. There are no known workarounds aside from upgrading.
How severe is CVE-2021-43861?: CVE-2021-43861 has a CVSS 3.x base score of 7.2, rated high severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-43861 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (56th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-43861?: CVE-2021-43861 affects Mermaid Project Mermaid. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-43861?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-43861 published?: CVE-2021-43861 was published on 2021-12-30 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:mermaid_project:mermaid:*:*:*:*:*:node.js:*:*

More vulnerabilities in Mermaid Project Mermaid

CVE-2025-54880 — Medium (CVSS 6.1): Mermaid is a JavaScript based diagramming and charting tool that uses Markdown-inspired text definitions and a renderer…
CVE-2021-35513 — Medium (CVSS 6.1): Mermaid before 8.11.0 allows XSS when the antiscript feature is used.
CVE-2026-41159 — Medium (CVSS 5.3): Mermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams and charts. Prior to 10.9.6…
CVE-2026-41150 — Medium (CVSS 5.3): Mermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams and charts. Prior to 10.9.6…
CVE-2022-31108 — Medium (CVSS 4.1): Mermaid is a JavaScript based diagramming and charting tool that uses Markdown-inspired text definitions and a renderer…

All CVEs affecting Mermaid Project Mermaid →

Other CWE-20 (Improper Input Validation) vulnerabilities

CVE-2026-48316 — Critical (CVSS 10.0): ColdFusion versions 2025.9, 2023.20 and earlier are affected by an Improper Input Validation vulnerability that could…
CVE-2026-48281 — Critical (CVSS 10.0): ColdFusion versions 2025.9, 2023.20 and earlier are affected by an Improper Input Validation vulnerability that could…
CVE-2026-48277 — Critical (CVSS 10.0): ColdFusion versions 2025.9, 2023.20 and earlier are affected by an Improper Input Validation vulnerability that could…
CVE-2026-48055 — Critical (CVSS 10.0): Streambert is a cross-platform Electron Desktop App to stream and download any video media. In versions 2.4.0 and…
CVE-2026-34910 — Critical (CVSS 10.0): A malicious actor with access to the network could exploit an Improper Input Validation vulnerability found in UniFi OS…
CVE-2026-33587 — Critical (CVSS 10.0): Lack of user input sanitisation in Open Notebook v1.8.3 allows the application user to execute Python code (and…

Browse all CWE-20 (Improper Input Validation) vulnerabilities →