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CVE-2026-52830

9.4 · CRITICAL

fast-mcp-telegram is a Telegram MCP Server.

Published Jul 2, 2026CWE-22EPSS 0.65%

Overview

CVE-2026-52830 is a critical-severity vulnerability. It was published on July 2, 2026 and has a CVSS 3.1 base score of 9.4 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.4, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

fast-mcp-telegram is a Telegram MCP Server. Prior to 0.19.1, fast-mcp-telegram validates HTTP Bearer tokens by joining the raw token string into a session-file path. The verifier rejects the exact reserved token telegram, but it does not reject path separators or normalize the path before checking whether the session file exists. A remote HTTP client can therefore authenticate as the default legacy session with a token such as ../fast-mcp-telegram/telegram when the documented default session file ~/.config/fast-mcp-telegram/telegram.session exists. This bypasses the reserved session name control that is intended to prevent HTTP multi-user sessions from colliding with the default stdio or legacy account. With account-prefixed MCP tools enabled, the attacker still sees and calls the prefixed tools for the default account, so the prefix middleware does not stop the session selection bypass. This vulnerability is fixed in 0.19.1.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/advisories/GHSA-rxw2-pc8j-vxwmRefweb.archive.org/web/20250926152207/https://github.com/leshchenko1979/fast-mcp-telegramGitHubgithub.com/advisories/GHSA-rxw2-pc8j-vxwm

How CyberStrike helps

Frequently asked questions

What is CVE-2026-52830?

CVE-2026-52830 is a critical-severity vulnerability. It was published on July 2, 2026 and has a CVSS 3.1 base score of 9.4 (CRITICAL).

How severe is CVE-2026-52830?

This vulnerability has a CVSS 3.1 base score of 9.4, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-52830?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-52830?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-52830 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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