Black: Arbitrary file writes from unsanitized user input in cache file name

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.7 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-32274: 0.65% estimated exploitation activity in the next 30 days; percentile 51.01 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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.

Published by the source

12 Mar 2026, 18:33 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 13:50 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-3936-cmfr-pm3m

2. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-3936-cmfr-pm3m

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-32274

Advisory: Black: Arbitrary file writes from unsanitized user input in cache file name
IDs: CVE-2026-32274, GHSA-3936-cmfr-pm3m
Record: https://patchnext.com/advisories/cve-2026-32274 (revision 3, source checked 26 Oct 2026, 13:50 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: black 26.3.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI black: affected >= 24.3.0, < 26.3.1; fixed in 26.3.1

## Suggested inspection (read-only)
- `python -m pip show black`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on black.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-3936-cmfr-pm3m (OSV record GHSA-3936-cmfr-pm3m lists affected ranges: PyPI black >=24.3.0 <26.3.1 (fixed))
- Verified: https://github.com/advisories/GHSA-3936-cmfr-pm3m (GitHub-reviewed advisory GHSA-3936-cmfr-pm3m lists affected ranges: PyPI black >=24.3.0 <26.3.1)

Commands are suggestions: review each one before running it.