The vulnerability lies in setuptools’ handling of MANIFEST.in exclusion directives. Prior to version 83.0.0, the tool matched compiled glob patterns against on‑disk filenames without applying Unicode normalization. On macOS file systems that use APFS or HFS+, an attacker could create a file in NFD form that matches an excluded pattern defined in NFC form, thereby bypassing the exclusion and having the file packaged into a source distribution. The result is that unintended files—potentially sensitive data or malicious code—are included in distributions that are later distributed or installed, exposing a moderate confidentiality and integrity risk explained by CWE‑1025, CWE‑176, and CWE‑697.

Any installation of the setuptools Python package with a version earlier than 83.0.0 running on macOS systems employing APFS or HFS+ systems is affected.

The CVSS score for this issue is 6.1, indicating moderate severity. The EPSS score is < 1% (0.0029), indicating a very low likelihood of exploitation, and the vulnerability is not listed in the CISA KEV catalog. Exploitation requires that the attacker have control over files on the filesystem used when building the source distribution—most commonly in a local developer or CI environment. The attack does not grant direct remote code execution but can lead to inclusion of malicious code upon installation by downstream users. The likely attack vector is a local build or CI pipeline on macOS that packages a source distribution without the latest version of setuptools.