CVE-2026-52830

CRITICALPre-NVD 9.49.4
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

This critical-severity CVE scores 9.4 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.6% (49th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source
Elevated
9.4EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.6%CVSS: 9.4Exploit: No code on recordExposed services: Not assessed

A fix is available — apply it.

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
9.4CRITICALmedium confidence
EG Risk
73
EG Risk 73/100

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed (value × EchelonGraph’s weight)
Severity94% × 45%
The EG Score, 9.4 of 10.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).
Exploitation public PoC (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.6%
EPSS %ILE
49th
KEV
Not listed

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation public PoC (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; 60 days if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

July 2, 2026

Last Modified

July 6, 2026

Advisory Details (2)

Auto-updated Oct 2, 2026
Patch available. Sources: github.
GitHub advisoryMentions a patch (unverified)

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
Web page

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

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.

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFix by version rangeDependents
fast-mcp-telegram0.0.1 ... 0.9.1 (55 versions)
  • every version up to 0.19.1: fixed in 0.19.1
—

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 14× in last 7d / 33× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 100 of 147 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 47 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  2. 2026-10-14 08:59 UTCEG score recompute
  3. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  4. 2026-10-13 05:35 UTCEG score recompute
  5. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  6. 2026-10-12 15:58 UTCEG score recompute
  7. 2026-10-11 19:41 UTCEG score recompute
  8. 2026-10-11 16:56 UTCEG score recompute
  9. 2026-10-11 14:19 UTCEG score recompute
  10. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  11. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  12. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  13. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  14. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  15. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  16. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  17. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  18. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  19. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  20. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  21. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  22. 2026-09-29 15:22 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  23. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  24. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  25. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.6% · 48th percentile
Show 75 more
  1. 2026-09-26 00:27 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  2. 2026-09-23 17:53 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  3. 2026-09-23 06:38 UTCEG score recompute
  4. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  5. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  6. 2026-09-18 06:14 UTCEG score recompute
  7. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  8. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  9. 2026-09-13 17:43 UTCEG score recompute
  10. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  11. 2026-09-13 08:59 UTCEG score recompute
  12. 2026-09-12 14:15 UTCEG score recompute
  13. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  14. 2026-09-10 09:35 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  15. 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  16. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  17. 2026-09-06 14:19 UTCEG score recompute
  18. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  19. 2026-09-05 23:52 UTCEG score recompute
  20. 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  21. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  22. 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  23. 2026-09-01 04:40 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  24. 2026-08-30 20:57 UTCEG score recompute
  25. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  26. 2026-08-30 11:22 UTCEG score recompute
  27. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  28. 2026-08-28 21:41 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  29. 2026-08-27 22:14 UTCEG score recompute
  30. 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  31. 2026-08-26 14:46 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  32. 2026-08-25 13:49 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  33. 2026-08-24 14:20 UTCEG score recompute
  34. 2026-08-24 10:15 UTCEG score recompute
  35. 2026-08-23 03:32 UTCEG score recompute
  36. 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  37. 2026-08-22 01:23 UTCEG score recompute
  38. 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  39. 2026-08-21 00:31 UTCEG score recompute
  40. 2026-08-20 22:55 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  41. 2026-08-20 04:01 UTCEG score recompute
  42. 2026-08-19 17:04 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  43. 2026-08-18 20:54 UTCEG score recompute
  44. 2026-08-18 13:48 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  45. 2026-08-17 14:16 UTCEG score recompute
  46. 2026-08-17 13:47 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  47. 2026-08-16 17:00 UTCEG score recompute
  48. 2026-08-16 14:56 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  49. 2026-08-16 04:48 UTCEG score recompute
  50. 2026-08-16 02:14 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  51. 2026-08-15 04:24 UTCEG score recompute
  52. 2026-08-15 01:30 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  53. 2026-08-13 23:56 UTCEG score recompute
  54. 2026-08-13 22:00 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  55. 2026-08-12 15:06 UTCEG score recompute
  56. 2026-08-12 13:51 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  57. 2026-08-11 14:41 UTCEG score recompute
  58. 2026-08-11 02:28 UTCEG score recompute
  59. 2026-08-11 00:00 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  60. 2026-08-09 13:47 UTCEG score recompute
  61. 2026-08-09 13:46 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  62. 2026-08-08 17:27 UTCEG score recompute
  63. 2026-08-08 16:37 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  64. 2026-08-07 17:03 UTCEG score recompute
  65. 2026-08-06 16:39 UTCEG score recompute
  66. 2026-08-06 13:47 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  67. 2026-08-05 20:13 UTCEG score recompute
  68. 2026-08-05 19:17 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  69. 2026-08-04 18:27 UTCEG score recompute
  70. 2026-08-04 15:10 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  71. 2026-08-04 14:20 UTCEG score recompute
  72. 2026-08-04 10:39 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  73. 2026-08-03 13:01 UTCEG score recompute
  74. 2026-08-03 10:36 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  75. 2026-08-02 04:47 UTCEG score recompute

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-52830?
CVE-2026-52830 is a critical-severity vulnerability; its CVE record was 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 the CVE record for CVE-2026-52830 published?
The CVE record for CVE-2026-52830 was published on July 2, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of July 6, 2026; the record at its source may have been updated since.
Is CVE-2026-52830 actively exploited?
CVE-2026-52830 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.6% probability of exploitation in the next 30 days (49th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-52830?
CVE-2026-52830 has a CVSS base score of 9.4 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-52830?
A fix for CVE-2026-52830 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-52830 are linked in the Vendor Advisories panel on this page.

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