CVE-2026-86439

HIGHPre-NVD 8.88.8—
EchelonGraph scoreHIGH confidence

Score 8.8 from GitHub Security Advisory (severity: HIGH) published 2026-09-08. the CNA's CVSS baseline 8.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:vulncheck, epss, ghsa
Trending — 3 sources updated this week
8.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 8.8Exploit: None knownExposed: 0

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

knowns versions before 0.30.0 fail to validate filesystem paths in MCP tool arguments, allowing attackers to read, create, overwrite and delete files outside the project directory. Attackers can supply path arguments containing directory traversal sequences to access arbitrary Markdown files accessible to the server process.

CVSS v3
8.8
EG Score
8.8(high)
EG Risk
40(Track)
EG Risk 40/100SSVC: Track

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
Severity88% × 45%
Exploitation1% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
64%
KEV
Not listed

Published

September 7, 2026

Last Modified

September 24, 2026

Advisory Details (6)

Auto-updated Sep 7, 2026
Patch available. Sources: github, github_commit, github_release.
generic

knowns before 0.30.0 Path Traversal via MCP doc and memory tools | Advisories | VulnCheck

https://www.vulncheck.com/advisories/knowns-before-0.30.0-path-traversal-via-mcp-doc-and-memory-tools
github_release Patch Available

v0.30.0

Patch available: knowns-dev/knowns v0.30.0

https://github.com/knowns-dev/knowns/releases/tag/v0.30.0
github_commit

commit 09c5a96fd581 (knowns-dev/knowns)

Fix landed in knowns-dev/knowns commit 09c5a96fd581 — awaiting tagged release

https://github.com/knowns-dev/knowns/commit/09c5a96fd5817b941dc86669278c1a17db10ed4e
generic

knowns/internal/storage/memory_store.go at v0.29.1 · knowns-dev/knowns · GitHub

https://github.com/knowns-dev/knowns/blob/v0.29.1/internal/storage/memory_store.go#L203-L211
generic

knowns/internal/storage/doc_store.go at v0.29.1 · knowns-dev/knowns · GitHub

https://github.com/knowns-dev/knowns/blob/v0.29.1/internal/storage/doc_store.go#L124-L129
github Patch Available

Unrestricted Path Traversal leading to out-of-bounds arbitrary .md file read, write, and deletion in MCP Docs + Memory Tools · Advisory · knowns-dev/knowns · GitHub

https://github.com/knowns-dev/knowns/security/advisories/GHSA-9gfj-28hw-jchp

Vendor Advisories for CVE-2026-86439(1)

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

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 26× in last 7d / 72× 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. 2026-09-25 03:39 UTCGHSA enrichment
  2. 2026-09-24 14:53 UTCEG score recompute
  3. 2026-09-24 14:53 UTCGHSA enrichment
  4. 2026-09-24 14:04 UTCEPSS rescore
  5. 2026-09-24 06:03 UTCEG score recompute
  6. 2026-09-24 06:03 UTCGHSA enrichment
  7. 2026-09-23 17:54 UTCEPSS rescore
  8. 2026-09-23 17:17 UTCGHSA enrichment
  9. 2026-09-23 04:32 UTCEG score recompute
  10. 2026-09-23 04:32 UTCGHSA enrichment
  11. 2026-09-22 16:01 UTCEPSS rescore
  12. 2026-09-22 15:46 UTCGHSA enrichment
  13. 2026-09-22 03:00 UTCEG score recompute
  14. 2026-09-22 03:00 UTCGHSA enrichment
  15. 2026-09-21 21:09 UTCEPSS rescore
  16. 2026-09-21 14:14 UTCGHSA enrichment
  17. 2026-09-21 01:28 UTCEG score recompute
  18. 2026-09-21 01:28 UTCGHSA enrichment
  19. 2026-09-20 20:16 UTCEPSS rescore
  20. 2026-09-20 12:30 UTCGHSA enrichment
  21. 2026-09-19 23:38 UTCEG score recompute
  22. 2026-09-19 23:38 UTCGHSA enrichment
  23. 2026-09-19 10:52 UTCGHSA enrichment
  24. 2026-09-18 22:05 UTCEG score recompute
  25. 2026-09-18 22:05 UTCGHSA enrichment
Show 47 more
  1. 2026-09-18 19:28 UTCEPSS rescore
  2. 2026-09-18 09:20 UTCGHSA enrichment
  3. 2026-09-17 20:33 UTCEG score recompute
  4. 2026-09-17 20:33 UTCGHSA enrichment
  5. 2026-09-17 19:32 UTCEPSS rescore
  6. 2026-09-17 07:47 UTCGHSA enrichment
  7. 2026-09-16 19:01 UTCEG score recompute
  8. 2026-09-16 19:01 UTCGHSA enrichment
  9. 2026-09-16 14:09 UTCEPSS rescore
  10. 2026-09-16 06:15 UTCEG score recompute
  11. 2026-09-16 06:15 UTCGHSA enrichment
  12. 2026-09-16 05:15 UTCEPSS rescore
  13. 2026-09-15 17:30 UTCGHSA enrichment
  14. 2026-09-15 04:42 UTCEG score recompute
  15. 2026-09-15 04:42 UTCGHSA enrichment
  16. 2026-09-15 03:12 UTCEPSS rescore
  17. 2026-09-15 03:12 UTCEPSS rescore
  18. 2026-09-14 15:53 UTCGHSA enrichment
  19. 2026-09-14 03:07 UTCEG score recompute
  20. 2026-09-14 03:07 UTCGHSA enrichment
  21. 2026-09-13 14:22 UTCGHSA enrichment
  22. 2026-09-13 01:37 UTCEG score recompute
  23. 2026-09-13 01:37 UTCGHSA enrichment
  24. 2026-09-12 12:51 UTCGHSA enrichment
  25. 2026-09-12 00:05 UTCEG score recompute
  26. 2026-09-12 00:05 UTCGHSA enrichment
  27. 2026-09-11 14:53 UTCEPSS rescore
  28. 2026-09-11 14:53 UTCEPSS rescore
  29. 2026-09-11 11:19 UTCEG score recompute
  30. 2026-09-11 11:18 UTCGHSA enrichment
  31. 2026-09-11 00:50 UTCGHSA enrichment
  32. 2026-09-10 12:05 UTCEG score recompute
  33. 2026-09-10 12:05 UTCGHSA enrichment
  34. 2026-09-09 23:17 UTCGHSA enrichment
  35. 2026-09-09 08:58 UTCEG score recompute
  36. 2026-09-09 08:58 UTCGHSA enrichment
  37. 2026-09-08 22:01 UTCEPSS rescore
  38. 2026-09-08 20:12 UTCGHSA enrichment
  39. 2026-09-08 13:44 UTCEG score recompute
  40. 2026-09-08 13:44 UTCGHSA enrichment
  41. 2026-09-08 13:01 UTCEG score recompute
  42. 2026-09-08 13:00 UTCGHSA enrichment
  43. 2026-09-08 12:24 UTCEG score recompute
  44. 2026-09-08 12:24 UTCGHSA enrichment
  45. 2026-09-07 23:35 UTCEG score recompute
  46. 2026-09-07 23:07 UTCEG score recompute
  47. 2026-09-07 23:06 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-86439?
CVE-2026-86439 is a high vulnerability published on September 7, 2026. knowns versions before 0.30.0 fail to validate filesystem paths in MCP tool arguments, allowing attackers to read, create, overwrite and delete files outside the project directory. Attackers can supply path arguments containing directory traversal sequences to access arbitrary Markdown files…
When was CVE-2026-86439 disclosed?
CVE-2026-86439 was first published in the National Vulnerability Database on September 7, 2026, with the most recent update on September 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-86439 actively exploited?
CVE-2026-86439 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 36.4% of all scored CVEs.
What is the CVSS score of CVE-2026-86439?
CVE-2026-86439 has a CVSS v4.0 base score of 8.8 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-86439?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-86439, 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.

Dependency Blast Radius

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