High severity · published Sep 7, 2026
CVE-2026-86439
knowns before 0.30.0 Path Traversal via MCP doc and memory tools
8.8
CVSS
1.1%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)1.1% · higher than 65% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
KN
knowns · knowns-dev
before 0.30.0 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-86439
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-86439
github.com
https://github.com/knowns-dev/knowns/blob/v0.29.1/internal/storage/doc_store.go#L124-L129
github.com
https://github.com/knowns-dev/knowns/blob/v0.29.1/internal/storage/memory_store.go#L203-L211
github.com
https://github.com/knowns-dev/knowns/commit/09c5a96fd5817b941dc86669278c1a17db10ed4e
github.com
https://github.com/knowns-dev/knowns/releases/tag/v0.30.0
github.com
https://github.com/knowns-dev/knowns/security/advisories/GHSA-9gfj-28hw-jchp
www.vulncheck.com
https://www.vulncheck.com/advisories/knowns-before-0.30.0-path-traversal-via-mcp-doc-and-memory-tools
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