Nezha 2.2.3 contains a Host header injection regression in the OAuth2 redirect endpoint

Why it is Amber

• CVSS 9.8 critical
• Remotely exploitable without logging in

References

• https://github.com/nezhahq/nezha/security/advisories/GHSA-rf68-8gjr-36q7
• https://www.vulncheck.com/advisories/nezha-through-2.2.3-host-header-injection-via-oauth2-redirect-uri
• https://github.com/nezhahq/nezha/security/advisories/GHSA-rf68-8gjr-36q7

Original description

Nezha 2.2.3 contains a Host header injection regression in the OAuth2 redirect endpoint. When the new optional dashboard_host setting is empty, /api/v1/oauth2/{provider} (cmd/dashboard/controller/oauth2.go) reflects the attacker-supplied HTTP Host header into the redirect_uri sent to the identity provider instead of falling back to the configured install_host. An attacker who induces a victim to begin OAuth2 login via a request that reaches Nezha with a forged Host header can cause an attacker-controlled callback URL to be used as the redirect_uri; if the OAuth2 provider accepts it, the victim's authorization code is delivered to the attacker origin, allowing the attacker to complete the OAuth2 login/binding flow and take over the account. This regresses the fix for GHSA-9rc6-8cjv-rcvx and is configuration-dependent (dashboard_host empty). At the time of the advisory no patched version was available.