Gogs is an open source self-hosted Git service. Prior to 0.14.3, (*Repository).UploadRepoFiles checks for symlinks only on the leaf of the upload target (osx.IsSymlink(targetPath)). The siblings UpdateRepoFile, DeleteRepoFile, and GetDiffPreview use hasSymlinkInPath, which lstats every component — UploadRepoFiles is the lone outlier. An attacker with repo-write access plus a multipart upload whose filename contains a literal backslash (preserved by filepath.Base on Linux, then converted to / by pathx.Clean) redirects the write through a previously-committed directory symlink. iox.CopyFile opens the destination with os.Create (no O_NOFOLLOW), so the kernel follows the parent symlink and writes attacker bytes anywhere the gogs UID can write — ~git/.ssh/authorized_keys → SSH foothold, or <repo>.git/hooks/post-receive → next-push RCE. This vulnerability is fixed in 0.14.3.

Affected: Go: gogs.io/gogs

Summary

`(*Repository).UploadRepoFiles` checks for symlinks only on the **leaf** of the upload target (`osx.IsSymlink(targetPath)`). The siblings `UpdateRepoFile`, `DeleteRepoFile`, and `GetDiffPreview` use `hasSymlinkInPath`, which lstats every component — `UploadRepoFiles` is the lone outlier. An attacker with repo-write access plus a multipart upload whose filename contains a literal backslash (preserved by `filepath.Base` on Linux, then converted to `/` by `pathx.Clean`) redirects the write through a previously-committed directory symlink. `iox.CopyFile` opens the destination with `os.Create` (no `O_NOFOLLOW`), so the kernel follows the parent symlink and writes attacker bytes anywhere the gogs UID can write — `~git/.ssh/authorized_keys` → SSH foothold, or `<repo>.git/hooks/post-receive` → next-push RCE.

Windows builds are unaffected: `filepath.Base` treats `\` as a separator (strips the multi-segment trick) and git defaults `core.symlinks=false` at checkout (committed mode-120000 entries become text files, not real symlinks). Details

The asymmetric check at `internal/database/repo_editor.go:601-612`:

```go targetPath := path.Join(dirPath, upload.Name) if osx.IsSymlink(targetPath) { // ← LEAF-ONLY return errors.Newf("cannot overwrite symbolic link: %s", upload.Name) } if err = iox.CopyFile(tmpPath, targetPath); err != nil { ... } ```

vs. `UpdateRepoFile`'s correct walker at `internal/database/repo_editor.go:163`:

```go if hasSymlinkInPath(…

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.