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GHSA-9f46-5r25-5wfm

CriticalCVSS 9.8 / 10
Published Jun 29, 2021·Last modified Mar 13, 2026
Affected Components(0)

No affected components available

Description

Impact

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:

  • 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.

Patches

The unicode whitespace removal has been replaced with a rejection (exception).

The library has been patched in:

  • 1.x: https://github.com/thephpleague/flysystem/commit/f3ad69181b8afed2c9edf7be5a2918144ff4ea32
  • 2.x: https://github.com/thephpleague/flysystem/commit/a3c694de9f7e844b76f9d1b61296ebf6e8d89d74

Workarounds

For 1.x users, upgrade to 1.1.4. For 2.x users, upgrade to 2.1.1.

Risk Scores
Base Score
9.8

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data. There is a high impact on the availability of the system.

Threat Intelligence
9.0

Active exploitation in the wild has been confirmed. Immediate patching or mitigation is required.

EPSS
3.49%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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Critical severity
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