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CVE-2021-32708— Time-of-check Time-of-use (TOCTOU) Race Condition in league/flysystem

Quick assessment

Affected
thephpleague flysystem
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Flysystem是一个开源文件存储库。 thephpleague flysystem存在代码注入漏洞，该漏洞源于在某些特定条件下，flysystem可能允许恶意用户远程执行代码。

CVSS 9.8 · Critical EPSS 3.49% · P89

Possible ATT&CK Techniques 1 AI

T1505.003 · Web Shell
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I. Basic Information for CVE-2021-32708

Vulnerability Information
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Vulnerability Title
Time-of-check Time-of-use (TOCTOU) Race Condition in league/flysystem
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
检查时间与使用时间(TOCTOU)的竞争条件
Source: CVE Program / CVE List V5
Vulnerability Title
thephpleague flysystem 代码注入漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Flysystem是一个开源文件存储库。 thephpleague flysystem存在代码注入漏洞，该漏洞源于在某些特定条件下，flysystem可能允许恶意用户远程执行代码。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
thephpleague flysystem < 1.1.4 -

II. Public POCs for CVE-2021-32708

# POC Description Source Link Shenlong Link
1 Affected versions of this package are vulnerable to Race Condition. 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. https://github.com/fazilbaig1/CVE-2021-32708 POC Details
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III. Intelligence Information for CVE-2021-32708

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Patches & Fixes for CVE-2021-32708 (2)

Vendor Advisories for CVE-2021-32708 (1)

Mailing List Discussions for CVE-2021-32708 (2)

Other References for CVE-2021-32708 (1)

IV. Related Vulnerabilities

Same product: flysystem
Same vendor: thephpleague
Same weakness: CWE-367

V. Comments for CVE-2021-32708

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