CVE-2026-55096
SSRF via DNS-resolution gap in _validate_url_security (file download by URL)
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.
| CWE | CWE-184 CWE-918 |
| Vendor | leshchenko1979 |
| Product | fast-mcp-telegram |
| Published | Sep 28, 2026 |
Get instant alerts for leshchenko1979 fast-mcp-telegram
Be the first to know when new high vulnerabilities affecting leshchenko1979 fast-mcp-telegram are published — delivered to Slack, Telegram or Discord.
CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N