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CVE-2021-43861

Incorrect sanitisation function leads to `XSS`

7.2 HighFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
High
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
High

Exploit likelihood

0.94%Up 0.1 points since Dec 31, 2021
90%50%10%1%

What each source reports

CVE List Score used 7.2

Incorrect sanitisation function leads to `XSS`

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.

Record
CVE-2021-43861
CVSS 3.1
7.2 HighCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-79, CWE-20
Updated
2026-11-02
EUVDEUVD-2022-0654 7.2

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.

Record
EUVD-2022-0654
CVSS 3.1
7.2 HighCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-03
GitHub AdvisoriesGHSA-p3rp-vmj9-gv6v 7.2

Incorrect sanitisation function leads to `XSS` in mermaid

Impact

Malicious diagrams can contain javascript code that can be run at diagram readers machines.

Patches

The users should upgrade to version 8.13.8

Workarounds

You need to upgrade in order to avoid this issue.

Record
GHSA-p3rp-vmj9-gv6v
CVSS 3.1
7.2 HighCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-20, CWE-79
Updated
2026-11-02
NVD 7.2

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.

Record
CVE-2021-43861
CVSS 3.1
7.2 HighCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
CVSS 3.1
5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
CVSS 2.0
3.5 LowAV:N/AC:M/Au:S/C:N/I:P/A:N
Weakness
CWE-20, CWE-79
Updated
2026-11-02
OSV 5.4

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.

Record
CVE-2021-43861
CVSS 3.1
5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Updated
2026-11-02
OSVDEBIAN-CVE-2021-43861 5.4

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.

Record
DEBIAN-CVE-2021-43861
CVSS 3.1
5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Updated
2026-11-02
OSVGHSA-p3rp-vmj9-gv6v 7.2

Incorrect sanitisation function leads to `XSS` in mermaid

Impact

Malicious diagrams can contain javascript code that can be run at diagram readers machines.

Patches

The users should upgrade to version 8.13.8

Workarounds

You need to upgrade in order to avoid this issue.

Record
GHSA-p3rp-vmj9-gv6v
CVSS 3.1
7.2 HighCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-20, CWE-79
Updated
2026-11-02
OSVUBUNTU-CVE-2021-43861 7.2

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.

Record
UBUNTU-CVE-2021-43861
CVSS 3.1
7.2 HighCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
CVSS 3.1
5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
mermaid
npm
 before 8.13.8
8.13.8
node-mermaid
Debian:14
 before 8.13.8+~cs10.4.16-1, plus listed versions
8.11.0+ds+~cs29.13.22-18.13.2+ds+~cs30.13.21-18.13.2+ds+~cs30.13.21-1.18.13.3+ds+~cs26.13.21-18.13.3+ds+~cs26.13.21-2
Show 6 moreShow less
8.7.0+ds+~cs27.17.17-18.7.0+ds+~cs27.17.17-28.7.0+ds+~cs27.17.17-2~bpo10+18.7.0+ds+~cs27.17.17-38.9.1+ds+~cs26.20.25-18.9.3+ds+~cs29.13.19-1
8.13.8+~cs10.4.16-1
node-mermaid
Ubuntu:22.04:LTS
 All versions, plus listed versions
8.7.0+ds+~cs27.17.17-38.13.3+ds+~cs26.13.21-18.13.3+ds+~cs26.13.21-28.13.8+~cs10.4.16-1
 None known
node-mermaid
Ubuntu:26.10
 All versions, plus listed versions
9.2.2+~2.0.0-19.2.2+~2.0.0-2
 None known

History

History
RecordedChangedSources
aliasesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-43861 is a high vulnerability (CVSS 7.2) in Mermaid-js Mermaid, published December 30, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.94%, the 61st percentile. Fixed in mermaid 8.13.8.

References

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