CVE-2026-52830

CRITICALPre-NVD 9.49.4—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.4 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4%, top 66% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Elevated
9.4
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 9.4Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
9.4
EG Score
9.4(medium)
EPSS
34.1%
KEV
Not listed

Published

July 2, 2026

Last Modified

July 6, 2026

Advisory Details (2)

Auto-updated Jul 2, 2026
Patch available. Sources: github.
generic

GitHub - leshchenko1979/fast-mcp-telegram: Telegram MCP Server. Multi-user, local and docker, error-resistant, easy web setup.

https://web.archive.org/web/20250926152207/https://github.com/leshchenko1979/fast-mcp-telegram
github Patch Available

fast-mcp-telegram: Bearer token path traversal bypasses reserved Telegram session protection · CVE-2026-52830 · GitHub Advisory Database · GitHub

https://github.com/advisories/GHSA-rxw2-pc8j-vxwm

Vendor Advisories for CVE-2026-52830(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 32× in last 7d / 32× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-07 03:18 UTCEG score recompute
  2. 2026-07-06 23:14 UTCEG score recompute
  3. 2026-07-06 19:09 UTCEG score recompute
  4. 2026-07-06 16:27 UTCEPSS rescore
  5. 2026-07-06 16:27 UTCEPSS rescore
  6. 2026-07-06 15:01 UTCEG score recompute
  7. 2026-07-06 10:55 UTCEG score recompute
  8. 2026-07-06 06:40 UTCEG score recompute
  9. 2026-07-06 02:36 UTCEG score recompute
  10. 2026-07-06 02:23 UTCEPSS rescore
  11. 2026-07-06 02:23 UTCEPSS rescore
  12. 2026-07-05 22:32 UTCEG score recompute
  13. 2026-07-05 18:28 UTCEG score recompute
  14. 2026-07-05 14:24 UTCEG score recompute
  15. 2026-07-05 10:20 UTCEG score recompute
  16. 2026-07-05 06:16 UTCEG score recompute
  17. 2026-07-05 02:30 UTCEPSS rescore
  18. 2026-07-05 02:11 UTCEG score recompute
  19. 2026-07-04 22:07 UTCEG score recompute
  20. 2026-07-04 18:03 UTCEG score recompute
  21. 2026-07-04 13:58 UTCEG score recompute
  22. 2026-07-04 09:51 UTCEG score recompute
  23. 2026-07-04 06:31 UTCEPSS rescore
  24. 2026-07-04 05:45 UTCEG score recompute
  25. 2026-07-04 01:39 UTCEG score recompute
Show 7 more
  1. 2026-07-03 21:33 UTCEG score recompute
  2. 2026-07-03 17:29 UTCEG score recompute
  3. 2026-07-03 13:25 UTCEG score recompute
  4. 2026-07-03 09:21 UTCEG score recompute
  5. 2026-07-03 05:17 UTCEG score recompute
  6. 2026-07-03 01:10 UTCEG score recompute
  7. 2026-07-02 21:06 UTCEG score recompute

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-52830?
CVE-2026-52830 is a critical vulnerability published on July 2, 2026. 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…
When was CVE-2026-52830 disclosed?
CVE-2026-52830 was first published in the National Vulnerability Database on July 2, 2026, with the most recent update on July 6, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-52830 actively exploited?
CVE-2026-52830 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 34.1% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-52830?
CVE-2026-52830 has a CVSS v3 base score of 9.4 (NVD).
How do I remediate CVE-2026-52830?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-52830, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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