GHSA-2fcr-jfvc-vgg2: Gitea: Two SSRF findings

| --- | --- | | Versions tested | gitea/gitea:1.26.2 (digest sha256:7d13848af12645600a5f9d93ee2560daa9c6fa6b5b859b7bff3a5e1c0b661031); gitea/gitea:latest resolves to the same digest at time of writing | | Source review | git checkout v1.26.2 (commit 2c749ce) | | Reproduction | bash run_poc.sh (single shot: brings up containers, runs three PoCs, prints captured evidence, tears down on exit) | | Files touched by the fixes | modules/hostmatcher/hostmatcher.go, modules/auth/openid/openid.go | Summary Gitea guards outbound HTTP from webhooks and repo migration with net.Dialer.Control, the correct hook point. The IP classifier behind it misses ten address families, of which CGNAT (100.64.0.0/10) is the practically important one because it is plain IPv4 and is used today by Tailscale, AWS VPC secondary CIDRs, and several Kubernetes pod-CIDR conventions. Any logged-in user can create a webhook pointing at an internal CGNAT host. The full HTTP response from that host (status, headers, body up to 1 MB) is stored in the webhook delivery log and rendered to the webhook owner on the hook detail page. The same gap applies to repo migration. Separately, the OpenID sign-in form at /user/login/openid fetches the user-supplied provider URL server-side via openid-go, which uses http.DefaultClient. No hostmatcher, no IP filter, no CSRF, no authentication. When OpenID sign-in is enabled, anyone on the internet can drive Gitea into making arbitrary GET requests against internal IPs. Both reproduce on gitea/gitea:1.26.2 (current stable) in default configuration. The bundled run_poc.sh reproduces all three primitives end-to-end in about one minute and tears the lab down at exit. Finding 1: hostmatcher classifier passes CGNAT and IPv6 transition prefixes The bug modules/hostmatcher/hostmatcher.go:107-119, the external builtin: case MatchBuiltinExternal: if ip.IsGlobalUnicast() && !ip.IsPrivate() { return true } IsGlobalUnicast() && !IsPrivate() was written for stack bookkeeping, no