CVE-2026-86540 json
knowns before 0.30.0 Arbitrary Code Execution via LSP Binary
published 2026-09-07 2 mo ago modified 2026-10-06 33 d ago also GHSA-mc52-mwq4-vfx3 , EUVD-2026-72558
- cvss
- 7.8
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 11%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- npm knowns 0.30.0
- knowns-dev knowns 0.30.0
CISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- no
- Technical impact
- total
- Assessed
- 2 mo ago
Exploit prediction
0.21% chance of exploitation in the next 30 days, higher than 11% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 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 |
| CNA | 3.1 | 7.8 | CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H |
| CNA | 4.0 | 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/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 |
| GitHub | 3.1 | 7.8 | CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| npm | knowns | <0.30.0 |
0.30.0 |
Affected products
- knowns-dev knowns
Classification
References
-
github.com
/knowns-dev/knowns/commit/d3989829fb5095666d23d005b2f78a082832a396
patch, web
-
github.com
/knowns-dev/knowns/security/advisories/GHSA-mc52-mwq4-vfx3
vendor-advisory, web
-
github.com
/knowns-dev/knowns/blob/v0.29.1/internal/lsp/detect.go#L128-L157
technical-description, web
-
github.com
/knowns-dev/knowns/blob/v0.29.1/internal/models/config.go#L205-L216
technical-description, web
-
github.com
/knowns-dev/knowns/releases/tag/v0.30.0
release-notes, web
-
vulncheck.com
/advisories/knowns-before-0.30.0-arbitrary-code-execution-via-lsp-binary
third-party-advisory, web
-
nvd.nist.gov
/vuln/detail/CVE-2026-86540
advisory
-
github.com
/knowns-dev/knowns
package
Sources
- CVE List CVE-2026-86540
- GitHub Advisory GHSA-mc52-mwq4-vfx3
- NVD CVE-2026-86540
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.