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CVE-2026-52830

fast-mcp-telegram: Bearer token path traversal bypasses reserved Telegram session protection

Published: Jul 2, 2026Updated: Jul 6, 2026 Sources: CVE List NVDCWE-22
9.4CRITICAL
NVD MITRE
EPSS Score
0.4%
Top 65.7%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
No Fix Available
Self-Check
Not available

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.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:HI:HA:L
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:LAvailability
Low
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Weaknesses

CWE-22CWE-287

Affected Products

leshchenko1979
fast-mcp-telegram

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.
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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

4 techniques
Collection
Discovery
Initial Access
View detailed technique mapping

References

https://github.com/advisories/GHSA-rxw2-pc8j-vxwm
github.com
https://web.archive.org/web/20250926152207/https://github.com/leshchenko1979/fast-mcp-telegram
web.archive.org
News mentions
1

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