CVE-2026-52830: fast-mcp-telegram is a Telegram MCP Server

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CRITICAL 9.4REMOTE

CVE-2026-52830 is a critical-severity flaw (CVSS 9.4) affecting affected software. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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-telegra

Why this priority

Critical severity
CISA SSVC: public proof of concept
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.4 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.6% (top 49%)
CISA exploited list	No
Weakness	CWE-22, CWE-287
Published	2026-07-02
Last modified	2026-10-25

Publisher (CNA): GitHub, Inc.

Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Timeline

2026-07-02 21:16 UTCPublished CVE record published
2026-10-25 21:10 UTCUpdated Record last modified

Exact fixes by distribution

Python (pip) · fast-mcp-telegram · FIXED · 0.19.1 · vulnerable: <= 0.19.0 · source

pip install --upgrade "fast-mcp-telegram>=0.19.1" pip show fast-mcp-telegram

Fedora 46 · rust-opendal-core · FIXED · 0.59.1-2.fc46 · FEDORA-2026-4607543819 · source

sudo dnf upgrade --advisory=FEDORA-2026-4607543819

Fedora ELN · velocitty · FIXED · 1.0.3-2.eln159 · FEDORA-2026-edae8cd295 · source

sudo dnf upgrade --advisory=FEDORA-2026-edae8cd295

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-52830?

No fixed release is listed yet. Watch the vendor advisory and apply any mitigation shown on this page.

Is CVE-2026-52830 being exploited?

CVE-2026-52830 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-52830 affect?

CVE-2026-52830 affects affected software. Severity is critical (CVSS 9.4). 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 re

How urgent is CVE-2026-52830?

Priority 54/100. Critical severity; CISA SSVC: public proof of concept; Remotely exploitable, no login, no user action

Software pages

Telegram vulnerabilities

References

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