CVE-2026-86439
published 2026-09-07CVE-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…
PriorityP260high8.8CVSS 3.1
AVNACLPRLUINSUCHIHAH
EPSS
1.08%
63.8th percentile
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.
Affected
2 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| knowns-dev | knowns | < 0.30.0 | 0.30.0 |
| knowns-dev | knowns | >= 0 < 0.30.0 | 0.30.0 |
CVSS provenance
nvdv3.18.8HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
nvdv4.08.7HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
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GHSA
Knowns Unrestricted Path Traversal leading to out-of-bounds arbitrary .md file read, write, and deletion in MCP Docs + Memory Tools
ghsa·2026-09-25
CVE-2026-86439 [HIGH] CWE-22 Knowns Unrestricted Path Traversal leading to out-of-bounds arbitrary .md file read, write, and deletion in MCP Docs + Memory Tools
Knowns Unrestricted Path Traversal leading to out-of-bounds arbitrary .md file read, write, and deletion in MCP Docs + Memory Tools
## Overview
Verified. Multiple **Unrestricted Path Traversal** vulnerabilities exist in the Knowns MCP `docs` and `memory` tools, allowing arbitrary file read, write, and deletion operations outside the project sandbox. The storage layer functions (`Get`, `Create`, `Update`, `Rename`, `Delete`) in both `doc_store.go` and `memory_store.go` concatenate user-controlled paths with `filepath.Join()` without any containment validation.
Additionally, the `docs.update` action with a `newPath` parameter performs a file deletion via `Rename()`, but is classified as `CapWrite` in the permission registry rather than `CapDelete`. This allows an attacker with a `read-wri
VulDB
knowns-dev knowns up to 0.29.x path traversal
vuldb·2026-09-08·CVSS 8.8
CVE-2026-86439 [HIGH] knowns-dev knowns up to 0.29.x path traversal
A vulnerability, which was classified as critical, was found in knowns-dev knowns up to 0.29.x. This vulnerability affects unknown code. Executing a manipulation can lead to path traversal.
This vulnerability appears as CVE-2026-86439. The attack may be performed from remote. There is no available exploit.
You should upgrade the affected component.
GHSA
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.
ghsa_unreviewed·2026-09-08
CVE-2026-86439 [HIGH] CWE-22 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.
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.
No detection rules found.
No public exploits indexed.
No writeups or analysis indexed.
https://github.com/knowns-dev/knowns/blob/v0.29.1/internal/storage/doc_store.go#L124-L129https://github.com/knowns-dev/knowns/blob/v0.29.1/internal/storage/memory_store.go#L203-L211https://github.com/knowns-dev/knowns/commit/09c5a96fd5817b941dc86669278c1a17db10ed4ehttps://github.com/knowns-dev/knowns/releases/tag/v0.30.0https://github.com/knowns-dev/knowns/security/advisories/GHSA-9gfj-28hw-jchphttps://www.vulncheck.com/advisories/knowns-before-0.30.0-path-traversal-via-mcp-doc-and-memory-tools
2026-09-07
Published