CVE-2026-55096: fast-mcp-telegram

The National Vulnerability Database (NVD) record says that before version 30.1 the send_message/send_message_to_phone Model Context Protocol (MCP) tools checked only a file URL's literal hostname, so a hostname resolving to a loopback, private or link-local address was fetched and its contents returned to the attacker as a Telegram attachment; fixed in 30.1.

The record

Kind

Vulnerability

Source record

CVE-2026-55096: fast-mcp-telegram is a Telegram MCP Server. Prior to version 30.1, the send_message/send_message_to_phone MCP (National Vulnerability Database record)

Record published

2026-09-28

Posted here

2026-10-12

World

Software agents · Enterprise work agents

Controls concerned

Hard domain restriction C-E2

Checked

Checked against its record on 2026-10-22 by a reader who did not draft it; report verification/reports/SIG-2026-10-12-006-2026-10-22.md.

A signal's controls are the ones its record points at, the exposure; a case's controls are the ones its records show were absent or failed, so the two can differ.

Corrections

Changes to what this signal says, with the reason. Every earlier version is kept.

• 2026-10-22: Summary. Found in an independent read against the record on 22 October 2026: the summary described the feature and never stated the vulnerability the record reports (CVE record CVE-2026-55096).
  Show the change

  Before: 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.

  After: The National Vulnerability Database (NVD) record says that before version 30.1 the send_message/send_message_to_phone Model Context Protocol (MCP) tools checked only a file URL's literal hostname, so a hostname resolving to a loopback, private or link-local address was fetched and its contents returned to the attacker as a Telegram attachment; fixed in 30.1.

What a signal is. A signal records what a primary record says; it assigns no fault. It is lighter than a case: one dated item from one record, tagged with the world, sector and controls it touches. It becomes a case when it meets the bar for one.

Newer: CVE-2026-90970: GitLab
Older: CVE-2026-55157: Token Optimizer MCP