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.
Published · last modified .
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.
EPSS exploit prediction
EPSS: 0.008 (56.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 57th percentile — 56.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.008 · newest: 0.008 · change: 0.000
Affected products
Weakness classification (CWE)
Public proof-of-concept exploits
References
- github.com/knowns-dev/knowns/security/advisories/GHSA-9h2q-r9fh-f98w (vendor-advisory)
- github.com/knowns-dev/knowns/blob/v0.30.0/internal/server/server.go (technical-description)
- github.com/knowns-dev/knowns/commit/37db0561b37b48b8bd035a417d7f1da6258ae657 (patch)
- github.com/knowns-dev/knowns/releases/tag/v0.31.0 (release-notes)
- www.vulncheck.com/advisories/knowns-before-0.31.0-external-control-of-agent-wor… (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.
- Is CVE-2026-88899 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.