---
cve: "CVE-2026-86439"
severity: "HIGH"
cvss: 8.7
epss: "1.1%"
vendor: "knowns-dev"
kev: false
exploited: false
published: "2026-09-07 23:16:53"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-11-02T11:34:50+01:00"
---

# CVE-2026-86439

> 8.7 HIGH · 🧪 PoC

## Beschreibung

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.

## CNA-Record (Kanon, cvelistV5)

- CNA: **VulnCheck**
- State: PUBLISHED
- Stand: 2026-09-24 14:21:21
- CNA-CVSS: **8.7** (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)

## CISA-Anreicherung (vulnrichment/ADP)

- CISA-SSVC (Coordinator, v2.0.3):
  - Exploitation: **none**
  - Automatable: **no**
  - Technical Impact: **total**

## CVSS-Vektor

```
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Gering | warn |
| UI Interaktion | Keine | bad |

## Schwachstellen-Klasse

- **CWE-22** — Improper Limitation of a Pathname to a Restricted Directory
  The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

## Angriffsmuster (CAPEC)

- [CAPEC-64 — Using Slashes and URL Encoding Combined to Bypass Validation Logic](https://capec.mitre.org/data/definitions/64.html) _(Severity: High)_
- [CAPEC-76 — Manipulating Web Input to File System Calls](https://capec.mitre.org/data/definitions/76.html) _(Severity: Very High)_
- [CAPEC-78 — Using Escaped Slashes in Alternate Encoding](https://capec.mitre.org/data/definitions/78.html) _(Severity: High)_
- [CAPEC-79 — Using Slashes in Alternate Encoding](https://capec.mitre.org/data/definitions/79.html) _(Severity: High)_
- [CAPEC-126 — Path Traversal](https://capec.mitre.org/data/definitions/126.html) _(Severity: Very High)_

## Patch verfügbar (OSV)

- cead30b2c3a34f66c0c40cb692ed51e588e63bd7 (Commit)
- 09c5a96fd5817b941dc86669278c1a17db10ed4e (Commit)

## Referenzen

- <https://github.com/knowns-dev/knowns/security/advisories/GHSA-9gfj-28hw-jchp>
- <https://github.com/knowns-dev/knowns/blob/v0.29.1/internal/storage/doc_store.go#L124-L129>
- <https://github.com/knowns-dev/knowns/blob/v0.29.1/internal/storage/memory_store.go#L203-L211>
- <https://github.com/knowns-dev/knowns/commit/09c5a96fd5817b941dc86669278c1a17db10ed4e>
- <https://github.com/knowns-dev/knowns/releases/tag/v0.30.0>
- <https://www.vulncheck.com/advisories/knowns-before-0.30.0-path-traversal-via-mcp-doc-and-memory-tools>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/sicherheitsluecken/cve-2026-86439/) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI WID (CSAF)_