CVE-2026-55096

Summary

fast-mcp-telegram is a Telegram MCP Server. Prior to version 30.1, the send_message/send_message_to_phone MCP tools accept files as a list of http(s) URLs, which the server downloads and attaches to the outgoing Telegram message. Downloads are guarded by _validate_url_security, an SSRF denylist that checks the URL's literal hostname string but never resolves DNS. The fetch (httpx.AsyncClient.get) does its own resolution at request time. Consequently a hostname that resolves to a loopback / private / link-local address passes the guard and is fetched — even with the secure defaults block_private_ips=True and allow_http_urls=False. Because the fetched body is returned to the attacker as a Telegram file attachment, this is a full-read, exfiltrating SSRF, not blind. This issue has been patched in version 30.1.

Affected Software

VendorProductVersion RangeStatus
leshchenko1979fast-mcp-telegram< 30.1affected

Weaknesses

  • CWE-184: CWE-184: Incomplete List of Disallowed Inputs
  • CWE-918: CWE-918: Server-Side Request Forgery (SSRF)

References