CVE-2021-32708 – Time-of-check Time-of-use (TOCTOU) Race Condition in league/flysystem

https://notcve.org/view.php?id=CVE-2021-32708

Flysystem is an open source file storage library for PHP. The whitespace normalisation using in 1.x and 2.x removes any unicode whitespace. Under certain specific conditions this could potentially allow a malicious user to execute code remotely. The conditions are: A user is allowed to supply the path or filename of an uploaded file, the supplied path or filename is not checked against unicode chars, the supplied pathname checked against an extension deny-list, not an allow-list, the supplied path or filename contains a unicode whitespace char in the extension, the uploaded file is stored in a directory that allows PHP code to be executed. Given these conditions are met a user can upload and execute arbitrary code on the system under attack. • https://github.com/thephpleague/flysystem/commit/a3c694de9f7e844b76f9d1b61296ebf6e8d89d74 https://github.com/thephpleague/flysystem/commit/f3ad69181b8afed2c9edf7be5a2918144ff4ea32 https://github.com/thephpleague/flysystem/security/advisories/GHSA-9f46-5r25-5wfm https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NWPTENBYKI2IG47GI4DHAACLNRLTWUR5 https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RNZSWK4GOMJOOHKLZEOE5AQSLC4DNCRZ https://packagist.org/packages/league/flysystem • CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition •