Improper Handling of Unicode Encoding in setuptools - CVE-2026-59890
Published: July 9, 2026
Vulnerability identifier: #VU137280
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-59890
CWE-ID: CWE-176
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Python Packaging Authority
Affected software:
setuptools
setuptools
Detailed vulnerability description
The vulnerability allows a remote attacker to disclose sensitive information.
The vulnerability exists due to improper handling of unicode encoding in setuptools FileList manifest exclusion matching when building a source distribution on normalization-preserving filesystems with Unicode filenames. A remote attacker can trick the victim into building and publishing a source distribution containing a specially named file to disclose sensitive information.
User interaction is required to build and publish the source distribution, and the issue is specific to Unicode normalization collisions such as NFC/NFD on macOS APFS or HFS+.
How to mitigate CVE-2026-59890
Install security update from vendor's website.