How severe is CVE-2021-32708?

CVE-2021-32708 has a CVSS score of 8.1/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-32708?

CVE-2021-32708 affects the following packages: league/flysystem (Packagist), league/flysystem (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2021-32708?

Update league/flysystem to 1.1.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-32708 is resolved across your whole dependency graph.

How do I detect CVE-2021-32708 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for league/flysystem, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2021-32708 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2021-32708 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-32708 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2021-32708?

CVE-2021-32708 has an EPSS (Exploit Prediction Scoring System) score of 3.5%, placing it in the 89th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2021-32708?

CVE-2021-32708 is classified as CWE-367 (CWE-367). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2021-32708 published, and has it been updated?

CVE-2021-32708 was published on June 24, 2021 and was last updated on July 8, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘

🐘 Packagist

Not in CISA KEV

HIGH severity

CVE-2021-32708 — flysystem

HIGHFix: thephpleague/flysystem@a3c694d

CVE-2021-32708 is a high-severity (CVSS 8.1) CWE-367 vulnerability in league/flysystem. A fix is available for league/flysystem — see the affected versions and patch details below.

Time-of-check Time-of-use (TOCTOU) Race Condition in league/flysystem

Also known asGHSA-9f46-5r25-5wfm

Published

Jun 24, 2021

Updated

Jul 8, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Oct 11, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

3.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs89th percentile — riskier than 89% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2021-32708 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

2 pkgs affected

🐘league/flysystem🐘league/flysystem

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

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:

Workarounds

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

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`league/flysystem`	all versions	1.1.4`composer require league/flysystem:^1.1.4`
🐘Packagist	`league/flysystem`	≥ 2.0.0&&< 2.1.1	2.1.1`composer require league/flysystem:^2.1.1`

Affected Products

2 products · 4 configurations

fedorafedoraproject

2 versions

3334

Application

flysystemthephpleague

≥ 2.0.0 && < 2.1.1

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for league/flysystem, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update league/flysystem to 1.1.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-32708 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### 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