CVE-2026-86439
CVE-2026-86439
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.
Vulnerability class: Path Traversal (Directory Traversal)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.011 (64.8th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 65th percentile — 64.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.008 · newest: 0.011 · change: +0.003
Weakness classification (CWE)
References
- DocStore.Get path join without containment (v0.29.1) (technical-description)
- MemoryStore.GetInLayer path join without containment (v0.29.1) (technical-description)
- knowns fix commit 09c5a96fd581 (patch)
- knowns v0.30.0 Release Notes (release-notes)
- GitHub Security Advisory (GHSA-9gfj-28hw-jchp) (vendor-advisory)
- VulnCheck Advisory: knowns before 0.30.0 Path Traversal via MCP doc and memory tools (third-party-advisory)
Frequently asked questions
- What is CVE-2026-86439?
- CVE-2026-86439 is a high-severity vulnerability, classified under Path Traversal. CVSS score: 8.8/10. Published 2026-09-07.
- How severe is CVE-2026-86439?
- High severity. CVSS v3 base score is 8.8 out of 10.