High severity · published Sep 28, 2026
CVE-2026-55096
SSRF via DNS-resolution gap in _validate_url_security (file download by URL)
7.1
CVSS
0.3%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
Low
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 17% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FA
fast-mcp-telegram · leshchenko1979
< 30.1 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-55096
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-55096
x_refsource_CONFIRM
https://github.com/leshchenko1979/fast-mcp-telegram/security/advisories/GHSA-xr72-j7vj-vp7g
x_refsource_MISC
https://github.com/leshchenko1979/fast-mcp-telegram/commit/e6b3032cfc906e14f5b84f2c2b8ec378eb457e57
x_refsource_MISC
https://github.com/leshchenko1979/fast-mcp-telegram/releases/tag/0.30.1
More from fast-mcp-telegram
9.4
CVE-2026-52830
fast-mcp-telegram: Bearer token path traversal bypasses reserved Telegram session protection
