CVE-2026-102601 Flysystem: WhitespacePathNormalizer's control-character (CorruptedPathDetected) check is bypassed by malformed UTF-8 in the path, affecting every adapter
Attackers can bypass path normalization checks using malformed UTF-8 to store files with hidden control characters, potentially spoofing terminal listings.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-102601?
CVE-2026-102601 is a low-severity path traversal vulnerability in thephpleague flysystem, published on 29 Sep 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-150
Which versions are affected by CVE-2026-102601?
2 open source packages ship an affected version, including league/flysystem.
| Package | Affected | Fixed in |
|---|---|---|
league/flysystem Packagist | All versions | 3.35.3 |
league/flysystem Packagist | All versions | 3.35.3 |
How do I fix CVE-2026-102601?
Upgrade league/flysystem to 3.35.3 or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-102601 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-102601 exists.
Sources
Also known as CLSA-2026-1790868478, CLSA-2026-1791742369, CLSA-2026-1791742447, DEBIAN-CVE-2026-102601, GHSA-cxf4-7mrp-vvpr, UBUNTU-CVE-2026-102601.