What is CVE-2026-88899?

CVE-2026-88899 is a critical-severity vulnerability in Knowns-Dev Knowns, classified under External Control of File Name or Path. CVSS score: 9.8/10. Published 2026-09-10.

How severe is CVE-2026-88899?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Vulnerability in Knowns-Dev Knowns

CVE-2026-88899

knowns versions before 0.31.0 fail to properly validate the x-opencode-directory request header in the /api/opencode proxy endpoint. Remote attackers can supply arbitrary directory paths to execute file operations outside the project root on the host system.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Affected products

Knowns-dev Knowns

Weakness classification (CWE)

CWE-73 — External Control of File Name or Path

References

disclosure@vulncheck.com (vendor-advisory)
disclosure@vulncheck.com (technical-description)
disclosure@vulncheck.com (patch)
disclosure@vulncheck.com (release-notes)
disclosure@vulncheck.com (third-party-advisory)

Frequently asked questions

What is CVE-2026-88899?: CVE-2026-88899 is a critical-severity vulnerability in Knowns-Dev Knowns, classified under External Control of File Name or Path. CVSS score: 9.8/10. Published 2026-09-10.
How severe is CVE-2026-88899?: Critical severity. CVSS v3 base score is 9.8 out of 10.