# CVE-2026-86540: knowns arbitrary binary execution via unvalidated LSP settings

Source: https://junglewise.ai/threats/cve-2026-86540-knowns-arbitrary-binary-execution-via-unvalidated-lsp-settings  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-07. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-86540 · Severity: high · CVSS 7.8 · Published 2026-09-07

knowns is a development tool that manages language server configuration for code editors. Versions before 0.30.0 fail to validate binary paths in project configuration files, allowing attackers to execute arbitrary programs with the user's privileges by committing a malicious configuration file to a repository. When a developer opens the repository, the attacker's binary is executed twice without any user warning or confirmation.

Technologies: [Knowns-Dev Knowns](https://junglewise.ai/threats/technologies/knowns), [knowns (npm)](https://junglewise.ai/threats/technologies/npm-knowns). Vendors: [Knowns-Dev](https://junglewise.ai/threats/vendors/knowns-dev), [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is CVE-2026-86540 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-86540 being exploited in the wild.

**How severe is CVE-2026-86540?** High severity, with a CVSS score of 7.8, published 7 September 2026.

**Which products and versions are affected?** Knowns-Dev Knowns before 0.30.0; knowns (npm) <= 0.29.1, SEMVER:introduced=0,fixed=0.30.0.

**Is there a fix for CVE-2026-86540?** Yes. knowns (npm): upgrade to 0.30.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-86540 attacked?** It is attacked with local access or from the adjacent network, in a software library.

**Am I affected by CVE-2026-86540?** Check whether you run Knowns-Dev Knowns or knowns (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- knowns (npm): upgrade to 0.30.0 or later

  ```sh
  npm install knowns@0.30.0
  ```


## Technical details

The vulnerability is a failure to validate the settings.lsp.languages binary field in .knowns/config.json project configuration files. The vulnerable code in internal/lsp/detect.go executes the binary path specified in the configuration without sanitizing or verifying it first. The attack vector is local/adjacent: an attacker commits a crafted .knowns/config.json to a shared repository; when any developer clones and opens the repository with knowns, the unvalidated binary path from the config is executed under the user's account. The attacker achieves arbitrary code execution under the developer's privileges. The issue was patched in version 0.30.0.

## Affected products

- knowns-dev knowns before 0.30.0

## Identifiers

- CVE-2026-86540
- GHSA-mc52-mwq4-vfx3

## Timeline

- 2026-09-07: disclosed
- 0.30.0: patched

## References

- [https://github.com/knowns-dev/knowns/blob/v0.29.1/internal/lsp/detect.go](https://github.com/knowns-dev/knowns/blob/v0.29.1/internal/lsp/detect.go)
- [https://github.com/knowns-dev/knowns/blob/v0.29.1/internal/models/config.go](https://github.com/knowns-dev/knowns/blob/v0.29.1/internal/models/config.go)

## Related threats

- [Knowns path traversal in workspace browse endpoint](https://junglewise.ai/threats/cve-2026-88940-knowns-path-traversal-in-workspace-browse-endpoint)
- [knowns path traversal in code.find MCP tool](https://junglewise.ai/threats/cve-2026-88938-knowns-path-traversal-in-code-find-mcp-tool)
- [knowns path traversal in code generation template engine](https://junglewise.ai/threats/cve-2026-88937-knowns-path-traversal-in-code-generation-template-engine)
- [Knowns path traversal in /api/opencode proxy endpoint](https://junglewise.ai/threats/cve-2026-88899-knowns-path-traversal-in-api-opencode-proxy-endpoint)
- [knowns path traversal in Document API](https://junglewise.ai/threats/cve-2026-86775-knowns-path-traversal-in-document-api)