Vulnerability · Published Sep 10, 2026 · Assigned by VulnCheck
CVE-2026-88899knowns before 0.31.0 External Control of Agent Working Directory via x-opencode-directory Header
Critical 9.8
In plain English
A critical-severity security flaw in knowns from knowns-dev. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.8% (higher than 57% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code.
Severity (CVSS 3.1)9.8Critical
Exploit odds (30 days)0.8%top 43.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack tooling1Public PoC
Official description
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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| knowns-dev | knowns | 0 – before 0.31.0 |
Weakness: CWE-73 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
References
- GitHub Security Advisory (GHSA-9h2q-r9fh-f98w) vendor-advisory
- https://github.com/knowns-dev/knowns/blob/v0.30.0/internal/server/server.go#L1283-L1296 technical-description
- https://github.com/knowns-dev/knowns/commit/37db0561b37b48b8bd035a417d7f1da6258ae657 patch
- knowns v0.31.0 Release Notes release-notes
- VulnCheck Advisory: knowns before 0.31.0 External Control of Agent Working Directory via x-opencode-directory Header third-party-advisory