{"id":"GHSA-qp9x-wp8f-qgjj","summary":"tuf has platform-dependent delegation path matching","details":"`DelegatedRole._is_target_in_pathpattern` uses `fnmatch.fnmatch` to decide whether a given target path is authorized by a delegation's glob pattern.\n\nPython's `fnmatch.fnmatch` calls `os.path.normcase()` on both arguments before matching. On POSIX hosts `normcase` is the identity function; on Windows hosts `os.path` resolves to `ntpath`, whose `normcase` lowercases its input and replaces `/` with `\\`.\n\nAs a result, python-tuf's delegation *path pattern* matching is case-sensitive on Linux/macOS but case-INSENSITIVE on Windows. This makes the authorization decision for a target dependent on the host operating system of the client running the updater.\n\nThe result on Windows is a TUF specification violation in the python-tuf `ngclient` implementation.\n\n## Vulnerable code\n\n`tuf/api/_payload.py` (HEAD `7ecb67d`):\n\n```python\n1183  @staticmethod\n1184  def _is_target_in_pathpattern(targetpath: str, pathpattern: str) -\u003e bool:\n1185      \"\"\"Determine whether ``targetpath`` matches the ``pathpattern``.\"\"\"\n1186      # We need to make sure that targetpath and pathpattern are pointing to\n1187      # the same directory as fnmatch doesn't threat \"/\" as a special symbol.\n1188      target_parts = targetpath.split(\"/\")\n1189      pattern_parts = pathpattern.split(\"/\")\n1190      if len(target_parts) != len(pattern_parts):\n1191          return False\n1192\n1193      # Every part in the pathpattern could include a glob pattern, that's why\n1194      # each of the target and pathpattern parts should match.\n1195      for target, pattern in zip(target_parts, pattern_parts, strict=True):\n1196          if not fnmatch.fnmatch(target, pattern):\n1197              return False\n1198      return True\n```\n\n`fnmatch.fnmatch` source (Python 3.12, unchanged in current mainline):\n\n```python\ndef fnmatch(name, pat):\n    ...\n    name = os.path.normcase(name)\n    pat = os.path.normcase(pat)\n    return fnmatchcase(name, pat)\n```\n\n## Fix\n\nReplace `fnmatch.fnmatch` with `fnmatch.fnmatchcase`, which is explicitly documented as \"not applying case normalization\", so it behaves identically across platforms.\n\n## Attack\n\n1. A TUF repository with two path-based delegations whose patterns differ only in case — for example, `Foo/*` and `foo/*`.\n2. The \"attacker\" delegation is listed BEFORE the \"legit\" delegation in the delegation order.\n3. The client searches for `foo/something`: on Windows, it will find the \"attacker\" provided target \"Foo/something\".\n\n\n## Exploitability caveats \n\n* The attack needs a repository configuration with case-colliding delegation path patterns. The attacker must control one of the delegated roles.\n* Delegation ordering matters: the attacker-controlled role must be visited BEFORE the legit role in the pre-order walk.\n* The client must run on Windows. No effect on Linux/macOS.\n\n## Credit\n\nReporter: Koda Reef @kodareef5 \nAdvisory edits: Jussi Kukkonen @jku","modified":"2026-09-10T03:51:06.938245876Z","published":"2026-05-28T22:46:13Z","database_specific":{"nvd_published_at":null,"cwe_ids":["CWE-178"],"severity":"MODERATE","github_reviewed":true,"github_reviewed_at":"2026-05-28T22:46:13Z"},"references":[{"type":"WEB","url":"https://github.com/theupdateframework/python-tuf/security/advisories/GHSA-qp9x-wp8f-qgjj"},{"type":"PACKAGE","url":"https://github.com/theupdateframework/python-tuf"},{"type":"WEB","url":"https://github.com/theupdateframework/python-tuf/releases/tag/v7.0.0"}],"affected":[{"package":{"name":"tuf","ecosystem":"PyPI","purl":"pkg:pypi/tuf"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"7.0.0"}]}],"versions":["0.10.0","0.10.1","0.10.2","0.11.0","0.11.1","0.11.2.dev1","0.11.2.dev2","0.11.2.dev3","0.11.dev0","0.12.0","0.12.1","0.12.2","0.12.dev0","0.12.dev1","0.12.dev2","0.13.0","0.14.0","0.15.0","0.16.0","0.17.0","0.18.0","0.18.1","0.19.0","0.20.0","0.7.5","0.9.8","0.9.9","1.0.0","1.1.0","2.0.0","2.1.0","3.0.0","3.1.0","3.1.1","4.0.0","5.0.0","5.1.0","6.0.0"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-qp9x-wp8f-qgjj/GHSA-qp9x-wp8f-qgjj.json","last_known_affected_version_range":"\u003c= 6.0.0"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"}]}