File Path Traversal in OpenCode Proxy Endpoint

Executive Summary

CVE-2026-88899 is a critical vulnerability in the Knowns npm package versions before 0.31.0. It allows unauthenticated attackers to bypass directory restrictions by injecting arbitrary paths via the x-opencode-directory header in the /api/opencode proxy endpoint. This enables file operations outside the intended project root, potentially accessing sensitive system directories like /root or /etc.

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Detection Guidance

Check Knowns version with: npm list knowns or knowns --version. If version is <= 0.30.0, the system is vulnerable. Inspect HTTP headers for requests to /api/opencode for x-opencode-directory header manipulation attempts.

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Impact Analysis

This vulnerability allows attackers to read, write, or execute files anywhere on the host system, leading to full host compromise. It can result in credential theft, file corruption, and arbitrary code execution through the AI agent's tool interface. The attack requires only network access to the Knowns server and no authentication.

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Compliance Impact

This vulnerability likely violates compliance requirements for data protection standards like GDPR and HIPAA due to unauthorized access to sensitive files and potential data breaches. It enables attackers to read or modify sensitive data, leading to regulatory penalties and loss of trust.

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Mitigation Strategies

Upgrade Knowns to version 0.31.0 or later immediately. If upgrading is not possible, disable the /api/opencode endpoint or implement strict input validation for the x-opencode-directory header.

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