leshchenko1979 fast-mcp-telegram up to 30.0 URL Validation httpx.AsyncClient.get server-side request forgery

Summaryinfo

A vulnerability described as critical has been identified in leshchenko1979 fast-mcp-telegram up to 30.0. Impacted is the function httpx.AsyncClient.get of the component URL Validation. The manipulation results in server-side request forgery. This vulnerability was named CVE-2026-55096. The attack may be performed from remote. There is no available exploit. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in leshchenko1979 fast-mcp-telegram up to 30.0. It has been classified as critical. Affected is the function httpx.AsyncClient.get of the component URL Validation. The manipulation with an unknown input leads to a server-side request forgery vulnerability. CWE is classifying the issue as CWE-918. The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-55096 since 06/16/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. There are known technical details, but no exploit is available.

Upgrading to version 30.1 eliminates this vulnerability.

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Productinfo

Type

• Artificial Intelligence Software

Vendor

• leshchenko1979

Name

• fast-mcp-telegram

Version

• 30.0

Website

• Product: https://github.com/leshchenko1979/fast-mcp-telegram/

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