CVE-2026-86439CWE-22path-traversal

CVE-2026-86439

High · published September 8, 2026

CVSS v3.1
8.8
EPSS
1%
Percentile
64.8
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
8.8 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CVSS v4.0
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
EPSS
0.01079 · 64.8th percentile
Weakness
CWE-22 · Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Published
2026-09-08T03:16Z
References (6)
https://github.com/knowns-dev/knowns/blob/v0.29.1/internal/storage/doc_store.go#L124-L129 · [email protected]https://github.com/knowns-dev/knowns/blob/v0.29.1/internal/storage/memory_store.go#L203-L211 · [email protected]https://github.com/knowns-dev/knowns/commit/09c5a96fd5817b941dc86669278c1a17db10ed4e · [email protected]https://github.com/knowns-dev/knowns/releases/tag/v0.30.0 · [email protected]https://github.com/knowns-dev/knowns/security/advisories/GHSA-9gfj-28hw-jchp · [email protected]https://www.vulncheck.com/advisories/knowns-before-0.30.0-path-traversal-via-mcp-doc-and-memory-tools · [email protected]
EPSS history
Timeline
  • 09 SEP 03:20Z
    EPSS moved — → 1%
    epss
  • 07 SEP 23:03Z
    knowns before 0.30.0 Path Traversal via MCP doc and memory tools
    cvelistv5