CVE-2026-52830Public exploitNetwork attack vector

Unauthenticated account access via bearer token traversal

Published Jul 2, 2026 · Updated Jul 2, 2026

Authentication bypass in fast-mcp-telegram before 0.19.1 allows remote attackers to access the default Telegram account via HTTP. SessionFileTokenVerifier.verify_token() appends an unvalidated bearer token to a session-file path and accepts a traversal alias for the reserved telegram session. Exposure requires HTTP authentication and an existing default telegram.session file; successful access permits reading messages, sending messages, and invoking available MTProto tools.

CVSS severity9.4
Critical
EPSS probability0.65%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in fast-mcp-telegram before 0.19.1 allows remote attackers to access the default Telegram account via HTTP. SessionFileTokenVerifier.verify_token() appends an unvalidated bearer token to a session-file path and accepts a traversal alias for the reserved telegram session. Exposure requires HTTP authentication and an existing default telegram.session file; successful access permits reading messages, sending messages, and invoking available MTProto tools.

The record

CVE
CVE-2026-52830
Published
Jul 2, 2026
Updated
Jul 2, 2026
Vendor
Alexey Leshchenko
Product
fast-mcp-telegram
Classifications
CWE-287, CWE-22, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 2, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 2, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 0.19.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Alexey Leshchenko · fast-mcp-telegramversion=< 0.19.1

Published CVSS scores

9.4GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-287Improper Authentication
CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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