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.

Project Subscriptions

Vendors Products
Leshchenko1979 Subscribe
Fast-mcp-telegram Subscribe
Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Mon, 28 Sep 2026 19:30:00 +0000

Type Values Removed Values Added
First Time appeared Leshchenko1979
Leshchenko1979 fast-mcp-telegram
Vendors & Products Leshchenko1979
Leshchenko1979 fast-mcp-telegram

Mon, 28 Sep 2026 17:00:00 +0000

Type Values Removed Values Added
Description 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.
Title SSRF via DNS-resolution gap in _validate_url_security (file download by URL)
Weaknesses CWE-184
CWE-918
References
Metrics cvssV3_1

{'score': 7.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N'}


Projects

Sign in to view the affected projects.

cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-09-28T16:38:26.730Z

Reserved: 2026-06-16T14:41:54.578Z

Link: CVE-2026-55096

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-09-28T17:17:50.007

Modified: 2026-09-28T17:17:50.007

Link: CVE-2026-55096

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-28T19:15:05Z

Weaknesses