{"id":"CVE-2021-32708","aliases":["GHSA-9f46-5r25-5wfm"],"url":"https://o3.security/vulnerability/CVE-2021-32708","summary":"Time-of-check Time-of-use (TOCTOU) Race Condition in league/flysystem","details":"### Impact\n\nThe 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.\n\nThe conditions: \n\n- A user is allowed to supply the path or filename of an uploaded file.\n- The supplied path or filename is not checked against unicode chars.\n- The supplied pathname checked against an extension deny-list, not an allow-list.\n- The supplied path or filename contains a unicode whitespace char in the extension.\n- The uploaded file is stored in a directory that allows PHP code to be executed.\n\nGiven these conditions are met a user can upload and execute arbitrary code on the system under attack.\n\n### Patches\n\nThe unicode whitespace removal has been replaced with a rejection (exception).\n\nThe library has been patched in:\n- 1.x: https://github.com/thephpleague/flysystem/commit/f3ad69181b8afed2c9edf7be5a2918144ff4ea32\n- 2.x: https://github.com/thephpleague/flysystem/commit/a3c694de9f7e844b76f9d1b61296ebf6e8d89d74\n\n### Workarounds\n\nFor 1.x users, upgrade to 1.1.4. For 2.x users, upgrade to 2.1.1.\n","published":"2021-06-24T17:15:08.263Z","modified":"2026-07-08T06:29:32.158588247Z","cvss":{"score":8.1,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Packagist","name":"league/flysystem","fixedVersion":"1.1.4"},{"ecosystem":"Packagist","name":"league/flysystem","fixedVersion":"2.1.1"}],"fix":{"url":"https://github.com/thephpleague/flysystem/commit/a3c694de9f7e844b76f9d1b61296ebf6e8d89d74","label":"thephpleague/flysystem@a3c694d"},"references":[{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NWPTENBYKI2IG47GI4DHAACLNRLTWUR5/"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RNZSWK4GOMJOOHKLZEOE5AQSLC4DNCRZ/"},{"type":"ADVISORY","url":"https://packagist.org/packages/league/flysystem"},{"type":"FIX","url":"https://github.com/thephpleague/flysystem/commit/a3c694de9f7e844b76f9d1b61296ebf6e8d89d74"},{"type":"FIX","url":"https://github.com/thephpleague/flysystem/commit/f3ad69181b8afed2c9edf7be5a2918144ff4ea32"},{"type":"FIX","url":"https://github.com/thephpleague/flysystem/security/advisories/GHSA-9f46-5r25-5wfm"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-32708"},{"type":"WEB","url":"https://github.com/FriendsOfPHP/security-advisories/blob/master/league/flysystem/CVE-2021-32708.yaml"},{"type":"PACKAGE","url":"https://github.com/thephpleague/flysystem"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/NWPTENBYKI2IG47GI4DHAACLNRLTWUR5"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/RNZSWK4GOMJOOHKLZEOE5AQSLC4DNCRZ"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-08T06:29:32.158588247Z"}}