knowns OS Command Injection via Insecure LSP Binary Path Config in .knowns/config.json

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.8 · CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS

• CVE-2026-86540: 0.21% estimated exploitation activity in the next 30 days; percentile 11.56 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Overview A critical Arbitrary Code Execution (ACE) vulnerability exists in the Knowns Language Server Protocol (LSP) detection and startup pipeline. The system blindly trusts the settings.lsp.languages.<lang.binary field defined in the project-level .knowns/config.json file. Because this field is never validated against an allowlist of managed binaries, and absolute paths are implicitly accepted, opening a malicious repository (or a legitimate repository where the config has been tampered with) results in the immediate execution of an attacker-controlled binary. The payload is executed twice per session: once during the initial runVersionCheck (health check), and again when the LSP server process is spawned via Server.Start(). When chained with the previously identified Config Overwrite vulnerabilities, this flaw yields a fully unauthenticated Remote Code Execution chain. Affected paths | File Path | Role | Vulnerability & Execution Impact | | :--- | :--- | :--- | |…

Published by the source

6 Oct 2026, 18:58 UTC

Last modified by the source

6 Oct 2026, 19:15 UTC

Source last checked

26 Oct 2026, 13:06 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-mc52-mwq4-vfx3

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-mc52-mwq4-vfx3

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-mc52-mwq4-vfx3

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# Patch Next advisory brief: CVE-2026-86540

Advisory: knowns OS Command Injection via Insecure LSP Binary Path Config in .knowns/config.json
IDs: CVE-2026-86540, GHSA-mc52-mwq4-vfx3
Record: https://patchnext.com/advisories/cve-2026-86540 (revision 3, source checked 26 Oct 2026, 13:06 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: knowns 0.30.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm knowns: affected <= 0.29.1; fixed in 0.30.0

## Suggested inspection (read-only)
- `npm ls knowns --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on knowns.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-mc52-mwq4-vfx3 (GitHub-reviewed advisory GHSA-mc52-mwq4-vfx3 lists affected ranges: npm knowns >=0 <=0.29.1)
- Verified: https://osv.dev/vulnerability/GHSA-mc52-mwq4-vfx3 (OSV record GHSA-mc52-mwq4-vfx3 lists affected ranges: npm knowns >=0 <0.30.0 (fixed))

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