GHSA-wv27-2vqp-j7g5: Gogs has the ability to import local repositories via Mirror Settings

Summary The Gogs Mirror Settings functionality provide an alternative way from the well protected New Migration functionality for any authenticated users to import local repositories. This issue stems from a lack of validation of SaveAddress function. Details Here is the function implementation of the secure New Migration functionality. <img width="1200" height="755" alt="image" src="https://github.com/user-attachments/assets/a6c2f307-715e-4451-bbc1-7bd934d56f96" /> Here is the function implementation of the Mirror Settings without any validation. <img width="1200" height="477" alt="image" src="https://github.com/user-attachments/assets/a11c41b8-1d08-499c-bce6-ab40844211d7" /> PoC The New Migration feature correctly blocked my attempt to import a local repository. <img width="1200" height="1008" alt="image" src="https://github.com/user-attachments/assets/dfc5aa3f-1cc4-427d-b7fe-274363c83c4e" /> But if I create a normal migration with a valid repository. <img width="1200" height="1006" alt="image" src="https://github.com/user-attachments/assets/c96b356e-8ca9-4e79-a69b-ff14593c0cac" /> Then, I could use the Mirror Settings feature under the Repository Settings sync a local repository. <img width="1200" height="476" alt="image" src="https://github.com/user-attachments/assets/9105475c-ae68-4d93-96d5-a3ec356deba7" /> Here is the result after the sync. <img width="1200" height="533" alt="image" src="https://github.com/user-attachments/assets/1df76642-3e55-4493-a422-f7f0619b463d" /> Impact Users can import local repositories from the server's filesystem, which allows accessing any repository the git user has access to. There is also a potential issue of blind SSRF.