Gitea · Gitea · CVE-2026-20896
**Name of the Vulnerable Software and Affected Versions**
Gitea Docker image versions prior to 1.26.3
**Description**
A configuration flaw in the official Docker images allows an unauthenticated remote attacker to impersonate any user, including administrators, by spoofing the `X-WEBAUTH-USER` header. This occurs because the `app.ini` template hard-codes the `REVERSE PROXY TRUSTED PROXIES` variable to a wildcard (`*`), instructing the application to trust identity headers from any source IP address rather than restricting them to a trusted reverse proxy. This issue is exploitable when reverse-proxy authentication is enabled. If auto-registration is also active, an attacker can impersonate arbitrary usernames that do not yet exist in the system. Approximately 22,900 unique hosts running Gitea were identified as externally accessible, with a significant portion potentially affected. Real-world reconnaissance and exploitation attempts were observed shortly after public disclosure. The flaw affects the web interface but does not impact the token-based API endpoints (e.g., `/api/v1/...`).
**Recommendations**
Update Gitea to version 1.26.4 or newer.
Replace the `REVERSE PROXY TRUSTED PROXIES = *` configuration with specific IP addresses of trusted reverse proxies.
Disable the `ENABLE REVERSE PROXY AUTHENTICATION` setting if reverse-proxy authentication is not required.
Disable user auto-registration if it is not necessary.
Restrict direct access to the Gitea HTTP port using firewalls or network isolation to ensure traffic only flows through the intended reverse proxy.