CVE-2021-32708 : Security Advisory and Response
Discover the details of CVE-2021-32708, a critical Time-of-check Time-of-use (TOCTOU) Race Condition vulnerability in Flysystem PHP library. Learn about the impact, affected versions, and mitigation steps.
An open source file storage library for PHP, Flysystem has a critical vulnerability that could allow remote code execution under specific conditions. Users are urged to upgrade to the patched versions to mitigate the risk.
Understanding CVE-2021-32708
This CVE highlights a Time-of-check Time-of-use (TOCTOU) Race Condition in league/flysystem, impacting versions < 1.1.4 and >= 2.0.0, < 2.1.1.
What is CVE-2021-32708?
Flysystem, a PHP library for file storage, contains a critical vulnerability due to the removal of unicode whitespace normalization. This flaw could enable a malicious user to execute remote code given certain conditions.
The Impact of CVE-2021-32708
The vulnerability, if exploited, could allow an attacker to upload and execute arbitrary code on the system, leading to severe consequences in terms of confidentiality, integrity, and availability.
Technical Details of CVE-2021-32708
This section provides an overview of the vulnerability specifics.
Vulnerability Description
A user can circumvent security measures under specific conditions, uploading and executing arbitrary code on vulnerable systems. The issue has been addressed in versions 1.1.4 and 2.1.1.
Affected Systems and Versions
Versions < 1.1.4 and >= 2.0.0, < 2.1.1 of Flysystem are affected by this vulnerability.
Exploitation Mechanism
The vulnerability arises from the lack of proper validation and handling of user-supplied filenames, leading to the execution of malicious code.
Mitigation and Prevention
To address CVE-2021-32708, users must take immediate actions and implement long-term security practices.
Immediate Steps to Take
Upgrade to Flysystem version 1.1.4 if using 1.x, and version 2.1.1 if using 2.x to mitigate the vulnerability.
Long-Term Security Practices
Enhance security practices by ensuring strict input validation, file upload restrictions, and regular security audits to prevent similar vulnerabilities.
Patching and Updates
Stay informed about security patches and updates for Flysystem to protect systems from potential exploitation.