CVE-2026-50553: Note Mark: Path traversal via unsanitized book/note slug in migrate export (sibling of GHSA-g49p)

Note Mark validates book and note slug values with the OpenAPI/huma tag pattern:"[a-z0-9-]+". huma compiles this with regexp.MustCompile(s.Pattern) and tests it with patternRe.MatchString(str), an UNANCHORED match. Because the pattern is not anchored (^...$), any string that merely CONTAINS one [a-z0-9-] substring passes validation. A slug such as ../../../../../../tmp/escape is accepted and stored verbatim.

The data-export CLI commands (note-mark migrate export and note-mark migrate export-v1) join these unsanitized slugs straight into the output path with path.Join / filepath.Join, then os.MkdirAll the directory and os.Create the note file. path.Join resolves the ../ segments, so the note content file is written OUTSIDE the configured export directory. The export process commonly runs as root (default in Docker / bare-metal admin usage), so this is a root-privilege arbitrary directory create + file write.

This is the unguarded sibling of GHSA-g49p-4qxj-88v3 (CVE class CWE-22 in the same export sinks). That fix added filepath.Base(asset.Name) to sanitize the asset filename, but the adjacent path components book.Slug and note.Slug — used in the very same path.Join calls in the same two export functions — were left raw, and their input-side pattern guard is bypassable as shown above.