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 cert...

Description

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. The unicode whitespace removal has been replaced with a rejection (exception). For 1.x users, upgrade to 1.1.4. For 2.x users, upgrade to 2.1.1.

Metrics

CVSS 3.1

8.1/10

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

3.49%

87.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Thephpleague	Flysystem	>= 1.0.0, < 1.1.4
Thephpleague	Flysystem	>= 2.0.0, < 2.1.1
Fedoraproject	Fedora	33
Fedoraproject	Fedora	34

References

https://github.com/thephpleague/flysystem/commit/a3c694de9f7e844b76f9d1b61296ebf6e8d89d74Patch, Third Party Advisory
https://github.com/thephpleague/flysystem/commit/f3ad69181b8afed2c9edf7be5a2918144ff4ea32Patch, Third Party Advisory
https://github.com/thephpleague/flysystem/security/advisories/GHSA-9f46-5r25-5wfmPatch, Third Party Advisory
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/flysystemProduct, Third Party Advisory
https://github.com/thephpleague/flysystem/commit/a3c694de9f7e844b76f9d1b61296ebf6e8d89d74Patch, Third Party Advisory
https://github.com/thephpleague/flysystem/commit/f3ad69181b8afed2c9edf7be5a2918144ff4ea32Patch, Third Party Advisory
https://github.com/thephpleague/flysystem/security/advisories/GHSA-9f46-5r25-5wfmPatch, Third Party Advisory
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/flysystemProduct, Third Party Advisory

Timeline

Published: Jun 24, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is 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. The unicode whitespace removal has been replaced with a rejection (exception). For 1.x users, upgrade to 1.1.4. For 2.x users, upgrade to 2.1.1.

How severe is CVE-2021-32708?

CVE-2021-32708 has a CVSS score of 8.1/10 (HIGH severity). The EPSS model estimates a 3.49% probability of exploitation in the next 30 days.

How do I fix CVE-2021-32708?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.