CVE-2026-55096
SSRF via DNS-resolution gap in _validate_url_security (file download by URL)
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.
INFO
Published Date :
Sept. 28, 2026, 5:17 p.m.
Last Modified :
Sept. 28, 2026, 5:17 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-55096
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Update fast-mcp-telegram to version 30.1.
- Apply the latest security patches for the server.
- Review and restrict outbound network access.
- Validate all external URL inputs.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-55096.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-55096 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-55096
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-55096 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-55096 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by [email protected]
Sep. 28, 2026
Action Type Old Value New Value 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. Added CVSS V3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N Added CWE CWE-184 Added CWE CWE-918 Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/55xxx/CVE-2026-55096.json">CVE-2026-55096</a> Added Reference https://github.com/leshchenko1979/fast-mcp-telegram/commit/e6b3032cfc906e14f5b84f2c2b8ec378eb457e57 Added Reference https://github.com/leshchenko1979/fast-mcp-telegram/releases/tag/0.30.1 Added Reference https://github.com/leshchenko1979/fast-mcp-telegram/security/advisories/GHSA-xr72-j7vj-vp7g