CVE-2026-101090: Nezha through 2.2.3 Host Header Injection via OAuth2 redirect_uri

Vulnerability summary

CVE-2026-101090 is a critical (CVSS 9.8) Open Redirect vulnerability in nezhahq nezha. EPSS estimates a 0.36% chance of exploitation in the next 30 days, higher than 28.3% of scored vulnerabilities.

Timeline

1. 27-09-2026
   PublishedVulnerability first disclosed.
2. 28-09-2026
   Last modifiedVulnerability information updated.

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.

• CWE-601URL Redirection to Untrusted Site ('Open Redirect')The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.