CVE-2026-102601 (CVSS 3.5)

Description

Flysystem is an open source file storage library for PHP. Prior to 3.35.3, the default WhitespacePathNormalizer in src/WhitespacePathNormalizer.php used by Filesystem across adapters calls preg_match with the u modifier and treats both false and 0 as falsy. A path containing malformed UTF-8 causes PCRE to return false, so paths that also contain control characters bypass CorruptedPathDetected::forPath() in normalizePath(). Filesystem::write() can store such names and Filesystem::listContents() can return the raw ANSI escape sequences, allowing hidden or spoofed terminal file listings when an administrator displays them. This issue is fixed in version 3.35.3.

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CVSS v3.1 Score

3.5

LOW

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N

EPSS — Exploit Prediction

0.0034

Probability of exploitation

0.27%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-150 CWE-150

References

Other References

https://github.com/thephpleague/flysystem/commit/ef4a9a557d769b5d472c403125716706a0d9cc77 https://github.com/thephpleague/flysystem/releases/tag/3.35.3 https://github.com/thephpleague/flysystem/security/advisories/GHSA-cxf4-7mrp-vvpr https://github.com/thephpleague/flysystem/security/advisories/GHSA-cxf4-7mrp-vvpr

Frequently Asked Questions

What is CVE-2026-102601? +

Flysystem is an open source file storage library for PHP. Prior to 3.35.3, the default WhitespacePathNormalizer in src/WhitespacePathNormalizer.php used by Filesystem across adapters calls preg_match with the u modifier and treats both false and 0 as falsy. A path containing malformed UTF-8 causes PCRE to return false, so paths that also contain control characters bypass CorruptedPathDetected::forPath() in normalizePath(). Filesystem::write() can store such names and Filesystem::listContents() can return the raw ANSI escape sequences, allowing hidden or spoofed terminal file listings when an administrator displays them. This issue is fixed in version 3.35.3. It has a CVSS v3.1 base score of 3.5 (LOW).

How severe is CVE-2026-102601? +

CVE-2026-102601 has a CVSS v3.1 score of 3.5 out of 10, rated LOW. This is a low-severity vulnerability with limited impact. The EPSS score is 0.0034, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-102601? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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