What is CVE-2026-55096?

CVE-2026-55096 is a high-severity vulnerability in Leshchenko1979 Fast-Mcp-Telegram, classified under Incomplete List of Disallowed Inputs. CVSS score: 7.1/10. Published 2026-09-28.

How severe is CVE-2026-55096?

High severity. CVSS v3 base score is 7.1 out of 10.

SSRF in Leshchenko1979 Fast-Mcp-Telegram

CVE-2026-55096

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.

Published 2026-09-28.

CVSS v3 metric

CVSS v3 base score 7.1 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Leshchenko1979 Fast-Mcp-Telegram — versions < 30.1

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-55096?: CVE-2026-55096 is a high-severity vulnerability in Leshchenko1979 Fast-Mcp-Telegram, classified under Incomplete List of Disallowed Inputs. CVSS score: 7.1/10. Published 2026-09-28.
How severe is CVE-2026-55096?: High severity. CVSS v3 base score is 7.1 out of 10.