Executive brief
copilot-api is a server that converts GitHub Copilot into an OpenAI/Anthropic-compatible API. A flaw in the token validation logic trusts reverse DNS lookups on hostnames provided by clients, allowing attackers to spoof legitimate hosts and bypass security checks. This could enable unauthorized API access without valid authentication credentials.
Technical details
The vulnerability exists in the /token endpoint's Header Handler component (copilot-api versions ≤0.7.0) and is classified as CWE-350 (Reliance on Reverse DNS Resolution for a Security-Critical Action). The flaw allows attackers to manipulate the Host header to forge reverse DNS lookups, bypassing authentication or authorization checks that incorrectly trust DNS resolution results. The attack requires network access and authentication privileges to trigger, but can lead to integrity violations and potential API access escalation. The vulnerability has been publicly disclosed; the vendor was contacted but did not respond with a patch.
Affected products
- ericc-ch copilot-api up to 0.7.0
Timeline
- 2026-04-23: disclosed: Vulnerability published to OSV/NVD
- 2026-04-02: disclosed: Public disclosure via GitHub issue August829/CVEP#32