CVE-2026-86439 knowns before 0.30.0 Path Traversal via MCP doc and memory tools
Attackers can exploit path traversal in knowns MCP tools to read, create, overwrite, or delete arbitrary files outside the project directory.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-86439?
CVE-2026-86439 is a high-severity path traversal vulnerability in knowns-dev knowns, published on 7 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
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.
Weakness: CWE-22
Which versions are affected by CVE-2026-86439?
2 open source packages ship an affected version, including knowns.
| Package | Affected | Fixed in |
|---|---|---|
knowns npm | All versions | 0.30.0 |
knowns npm | All versions | 0.30.0 |
How do I fix CVE-2026-86439?
Upgrade knowns to 0.30.0 or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-86439 being exploited?
There is no known exploitation of CVE-2026-86439 in the wild and no public exploit code.
Sources
Also known as GHSA-9gfj-28hw-jchp.