# CVE-2026-86540 — knowns-dev knowns

> As of 2026-09-08, CVE-2026-86540 is a HIGH-severity vulnerability in knowns-dev knowns, CVSS v3.1 7.8, EPSS 0.1% (4.0th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-86540 as of 2026-09-08; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-09-08

## What is CVE-2026-86540?

knowns versions before 0.30.0 fail to validate the settings.lsp.languages binary field in project configuration files, allowing attackers to execute arbitrary binaries by crafting a malicious .knowns/config.json file. When a repository with a crafted configuration is opened, the unvalidated binary path is executed twice under the user's account without any verification.

The record classifies CVE-2026-86540 under weakness class [CWE-78](https://intel.threadlinqs.com/cwe/CWE-78). Its CVSS v3 base vector states that the flaw requires local access to the host, needs no prior authentication, needs a user to take an action first, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 28 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 7.8 — HIGH (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **CVSS v4.0 base score:** 8.5 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **EPSS (FIRST):** 0.1% probability of exploitation in the next 30 days, higher than 4.0% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 4.1/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-09-07, last modified 2026-09-08

## Is CVE-2026-86540 being exploited?

It currently carries a trending score of 31 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [knowns-dev](https://intel.threadlinqs.com/vendors/knowns-dev): knowns

## How to fix CVE-2026-86540

No vendor patch reference has been recorded for CVE-2026-86540 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-86540

No threat campaign in the Threadlinqs corpus currently references CVE-2026-86540, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, NVD, GitHub Security Advisories, FIRST EPSS. Last verified by Threadlinqs on 2026-09-08. This product uses the NVD API but is not endorsed or certified by the NVD.

**Vendor advisory and patch**

- [github.com — vendor advisory](https://github.com/knowns-dev/knowns/security/advisories/GHSA-mc52-mwq4-vfx3)
- [github.com — patch](https://github.com/knowns-dev/knowns/commit/d3989829fb5095666d23d005b2f78a082832a396)
- [github.com — release notes](https://github.com/knowns-dev/knowns/releases/tag/v0.30.0)

**Technical analysis**

- [github.com — technical description](https://github.com/knowns-dev/knowns/blob/v0.29.1/internal/lsp/detect.go#L128-L157)
- [github.com — technical description (config)](https://github.com/knowns-dev/knowns/blob/v0.29.1/internal/models/config.go#L205-L216)

**Third-party advisory**

- [vulncheck.com — third party advisory](https://www.vulncheck.com/advisories/knowns-before-0.30.0-arbitrary-code-execution-via-lsp-binary)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-86540
Full detection coverage and IOCs for threats exploiting CVE-2026-86540 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp