CVE-2021-32708Network attack vector

Remote code execution via Unicode whitespace stripping

Published Jun 24, 2021 · Updated Aug 3, 2024

Path normalization in The PHP League Flysystem before 1.1.4 and 2.0.0 through 2.1.0 allows remote attackers to execute PHP code. WhitespacePathNormalizer removes Unicode control characters from an attacker-supplied path, allowing a denied extension containing such a character to become executable after validation. Exploitation requires control of an uploaded path or filename, extension deny-list validation without prior Unicode rejection, and storage in a PHP-executable directory.

CVSS severity9.8
Critical
EPSS probability3.49%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Path normalization in The PHP League Flysystem before 1.1.4 and 2.0.0 through 2.1.0 allows remote attackers to execute PHP code. WhitespacePathNormalizer removes Unicode control characters from an attacker-supplied path, allowing a denied extension containing such a character to become executable after validation. Exploitation requires control of an uploaded path or filename, extension deny-list validation without prior Unicode rejection, and storage in a PHP-executable directory.

The record

CVE
CVE-2021-32708
Published
Jun 24, 2021
Updated
Aug 3, 2024
Vendor
The PHP League
Product
Flysystem
Classifications
CWE-367, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 24, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.1.4
  2. Affected versionversion=>= 2.0.0, < 2.1.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The PHP League · Flysystemversion=< 1.1.4; version=>= 2.0.0, < 2.1.1

Published CVSS scores

8.1NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
9.8GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-367Time-of-check Time-of-use (TOCTOU) Race Condition
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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