typo3/cms-core: Path Allowance Check Bypass in GeneralUtility::isAllowedAbsPath()
The path allowance check in GeneralUtility::isAllowedAbsPath() performed a plain string prefix comparison without requiring a directory separator boundary, causing a path like /var/www/html-other/secret.
What changed
The path allowance check in GeneralUtility::isAllowedAbsPath() performed a plain string prefix comparison without requiring a directory separator boundary, causing a path like /var/www/html-other/secret.yaml to be incorrectly accepted as valid when the project root was /var/www/html.
Who it affects
Administrator users with access to the File Abstraction Layer who can create new file storage definitions pointing to directories outside the project root.
What to do today
Update to TYPO3 versions 10.4.57 ELTS, 11.5.51 ELTS, 12.4.46 ELTS, 13.4.31 LTS, or 14.3.3 LTS that fix the problem.