CVE-2021-32708 Time-of-check Time-of-use (TOCTOU) Race Condition in league/flysystem
A race condition in Flysystem allows remote code execution if specific upload and storage configurations are present.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2021-32708?
CVE-2021-32708 is a critical vulnerability in Fedoraproject Fedora, published on 24 Jun 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-367
Which versions are affected by CVE-2021-32708?
4 open source packages ship an affected version, including league/flysystem. It affects 2 products.
| Package | Affected | Fixed in |
|---|---|---|
league/flysystem Packagist | All versions | 1.1.4 |
league/flysystem Packagist | All versions | 1.1.4 |
league/flysystem Packagist | From 2.0.0 | 2.1.1 |
league/flysystem Packagist | From 2.0.0 | 2.1.1 |
Products include Fedoraproject Fedora, Thephpleague Flysystem.
How do I fix CVE-2021-32708?
Upgrade league/flysystem to a fixed version for your release line: 1.1.4 or 2.1.1.
Is CVE-2021-32708 being exploited?
There is no known exploitation of CVE-2021-32708 in the wild and no public exploit code.
Public exploit code: 1 proofs of concept on GitHub.
Other vulnerabilities in Fedoraproject Fedora
Sources
Also known as CLSA-2026-1777596493, CLSA-2026-1777596494, DEBIAN-CVE-2021-32708, GHSA-9f46-5r25-5wfm, UBUNTU-CVE-2021-32708.