---
id: CVE-2026-32274
aliases:
  - GHSA-3936-cmfr-pm3m
  - PYSEC-2026-2121
title: 'Black: Arbitrary file writes from unsanitized user input in cache file name'
summary: 'Black: Arbitrary file writes from unsanitized user input in cache file name'
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N'
vendor: black
product: black
ecosystem: pip
affected:
  - 'black >= 24.3.0, < 26.3.1'
patched:
  - black 26.3.1
published: '2026-03-12'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T03:50:36.703011526Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-3936-cmfr-pm3m'
references:
  - url: 'https://github.com/psf/black/security/advisories/GHSA-3936-cmfr-pm3m'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-32274'
  - url: 'https://github.com/psf/black/pull/4176'
  - url: 'https://github.com/psf/black/pull/5038'
  - url: >-
      https://github.com/psf/black/commit/4937fe6cf241139ddbfc16b0bdbb5b422798909d
  - url: >-
      https://github.com/psf/black/commit/ed770ba4dd50c419148a0fca2b43937a7447e1f9
  - url: 'https://access.redhat.com/errata/RHSA-2026:10184'
  - url: 'https://access.redhat.com/errata/RHSA-2026:13545'
  - url: 'https://access.redhat.com/errata/RHSA-2026:13553'
  - url: 'https://access.redhat.com/security/cve/CVE-2026-32274'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2447111'
  - url: 'https://github.com/psf/black'
  - url: 'https://github.com/psf/black/releases/tag/26.3.1'
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/black/PYSEC-2026-2121.yaml
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-32274.json
tags:
  - osv
  - pip
epss: 0.00716
epssPercentile: 0.51687
ingestedAt: '2026-07-13T18:57:51.775Z'
---

## Overview

### Impact

Black writes a cache file, the name of which is computed from various formatting options. The value of the `--python-cell-magics` option was placed in the filename without sanitization, which allowed an attacker who controls the value of this argument to write cache files to arbitrary file system locations. 

### Patches

Fixed in Black 26.3.1.

### Workarounds

Do not allow untrusted user input into the value of the `--python-cell-magics` option.

## Affected packages

- `black >= 24.3.0, < 26.3.1`

## Remediation

Upgrade to a patched release:

- `black 26.3.1`