GHSA-jp7c-wj6q-3qf2 Gogs vulnerable to arbitrary file deletion via Path Traversal in wiki page update

• Go gogs.io/gogs: < 0.13.4 → fixed in 0.13.4

Summary A Path Traversal vulnerability exists in the `updateWikiPage` function of Gogs. The vulnerability allows an authenticated user with write access to a repository's wiki to delete arbitrary files on the server by manipulating the `old_title` parameter in the wiki editing form. Vulnerability Deatils The vulnerability is located in `internal/database/wiki.go`. When updating a wiki page, the application accepts an `old_title` parameter to identify the potential rename operation. This parameter is used directly in `path.Join` and `os.Remove` without proper sanitization. Code snippet from `internal/database/wiki.go`: ```go // Line 114 os.Remove(path.Join(localPath, oldTitle+".md")) ``` If an attacker provides a path traversal sequence (e.g., `../../../../target`) as `old_title`, the `os.Remove` function will resolve the path relative to the wiki's local directory and delete the target file. The vulnerability is limited to deleting files that end with `.md` (due to the appended extension), but depending on the filesystem and specific `path.Join` behavior, or if critical `.md` files exist (e.g. documentation, other wikis), the impact is significant. Additionally, in some contexts, the extension might be bypassed or ignored. Impact • Denial of Service: Deletion of critical configuration files or data (if they match the extension or via other tricks). • Data Loss: Deletion of other users' wiki pages or documentation. Remediation Sanitize the `oldTitle` parameter using `ToWikiPageName` (or `path.Clean` and basename validation) before using it in file operations, similar to how the new `title` is currently handled. ```go // Recommended Fix if oldTitle != "" { oldTitle = ToWikiPageName(oldTitle) } ``` Reproduction Steps 1. Log in to Gogs as a user with write access to a repository wiki. 2. Intercept the `POST` request to `/repo/wiki/edit`. 3. Modify the `old_title` parameter to `../../../../tmp/target_file`. 4. Submit the request. 5. Observe that `/tmp/target_file.md` is deleted from the server.