Gogs is an open source self-hosted Git service. Prior to 0.14.3, a Server-Side Request Forgery (SSRF) vulnerability exists in the repository migration functionality. The application validates only the initially submitted URL hostname, but git clone --mirror follows HTTP redirects. An authenticated user can submit a public URL that redirects to a blocked internal endpoint (e.g., 127.0.0.1), importing the internal repository's contents into an attacker-controlled repository. This vulnerability is fixed in 0.14.3.

Affected: Go: gogs.io/gogs

# Migration URL validation bypass via HTTP redirect to blocked internal endpoints

## Summary

A Server-Side Request Forgery (SSRF) vulnerability exists in the repository migration functionality. The application validates only the initially submitted URL hostname, but `git clone --mirror` follows HTTP redirects. An authenticated user can submit a public URL that redirects to a blocked internal endpoint (e.g., `127.0.0.1`), importing the internal repository's contents into an attacker-controlled repository.

## Vulnerability Details

The vulnerability is located in `internal/form/repo.go`. `ParseRemoteAddr()` validates the clone address hostname against a blocklist of local and private-network addresses. However, the actual migration is performed by `git clone --mirror` in `internal/database/repo.go`, which follows HTTP redirects without revalidation:

1. Attacker submits `http://attacker.example/redirect.git` — passes validation (public hostname). 2. Attacker's server responds with `302` redirect to `http://127.0.0.1:18081/victim/private.git`. 3. Git follows the redirect and clones the internal repository. 4. Gogs imports the cloned contents into the attacker's new repository.

The root cause is that Gogs validates only the initial URL and does not revalidate the final redirect target.

## Impact

This vulnerability bypasses the intended localhost/private-network migration restriction. Any authenticated user who can migrate repositories can import contents from internal Git…

Ein Angreifer kann mehrere Schwachstellen in Gogs ausnutzen, um erweiterte Berechtigungen zu erlangen, beliebigen Code auszuführen – sogar mit erweiterten Berechtigungen, was zur vollständigen Kontrolle über das System führen kann –, Sicherheitsmaßnahmen zu umgehen, Daten zu manipulieren, Cross-Site-Scripting-Angriffe durchzuführen, Benutzer auf bösartige Websites umzuleiten oder einen Denial-of-Service-Zustand zu verursachen.