JavaScript execution via unescaped mcp parameter
Published Aug 13, 2026 · Updated Aug 13, 2026
Reflected XSS in Next AI Draw.io 0.2.1 through 0.4.16 allows remote attackers to execute JavaScript via a crafted mcp URL. The embedded MCP HTTP server passes the mcp query value to getHtmlPage(), which inserts it unescaped into an inline JavaScript string and raw HTML. Exploitation requires the local MCP server to be running and a user to visit an attacker-controlled page; the resulting script can read and alter diagram sessions through localhost APIs.
Summary
What happened
Reflected XSS in Next AI Draw.io 0.2.1 through 0.4.16 allows remote attackers to execute JavaScript via a crafted mcp URL. The embedded MCP HTTP server passes the mcp query value to getHtmlPage(), which inserts it unescaped into an inline JavaScript string and raw HTML. Exploitation requires the local MCP server to be running and a user to visit an attacker-controlled page; the resulting script can read and alter diagram sessions through localhost APIs.
The record
- CVE
- CVE-2026-73037
- Published
- Aug 13, 2026
- Updated
- Aug 13, 2026
- Vendor
- Dayuan Jiang
- Product
- Next AI Draw.io
- Classifications
- CWE-79, T1189
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 13, 2026CVE publishedPublication date reported by the CVE source.
- Aug 13, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0.2.1 <=0.4.16
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Reflected XSS mcp parameter proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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