Mermaid improperly sanitizes of sequence diagram labels leading to XSS

published 2025-08-19 14 mo ago modified 2026-08-07 3 mo ago also EUVD-2025-28574 , GHSA-7rqq-prvp-x9jh

cvss: 5.3; version 4.0, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.8%; EPSS 0.8% chance of exploitation in 30 days, percentile 56%
public exploits: 0; none known

Mermaid is a JavaScript based diagramming and charting tool that uses Markdown-inspired text definitions and a renderer to create and modify complex diagrams. In the default configuration of mermaid 10.9.0-rc.1 to 11.9.0, user supplied input for sequence diagram labels is passed to innerHTML during calculation of element size, causing XSS.

Patch / fix

fixed in 2 links 2

npm mermaid 10.9.4, 11.10.0
mermaid_project mermaid 11.10.0

github.com/mermaid-js/mermaid@5c69e5f commit
github.com/mermaid-js/mermaid@685516a commit

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-54881 updated 2025-11-21 cvss 6.3

mermaid: Mermaid cross site scripting

Red Hat All currently supported Red Hat products
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation: Proof of concept is public
Automatable: yes
Technical impact: partial
Assessed: 14 mo ago (2025-08-19)

Exploit prediction

0.80% chance of exploitation in the next 30 days, higher than 56% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	4.0	5.3	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
CNA	4.0	5.3	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected packages

ecosystem	package	affected	fixed in
npm	mermaid	>=11.0.0-alpha.1, <11.10.0 >=10.9.0-rc.1, <10.9.4	11.10.0 10.9.4

Affected products

mermaid-js mermaid

Classification

Weakness

CWE-79 Improper Neutralization of Input During Web Page Generation

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.

Summary