CVE-2026-32274: Black Arbitrary File Writes From Unsanitized Vulnerability

HIGH
Advisory Identifier: GHSA-3936-cmfr-pm3m
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CVSS 7.5
CWE-22
Published
Advisory Summary

CVE-2026-32274 is a HIGH (CVSS 7.5) arbitrary file writes from unsanitized vulnerability (CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')) affecting Black libraries in the PyPI ecosystem. The issue involves arbitrary file writes from unsanitized user input in cache file name. Remediation is available by upgrading affected packages to version 26.3.1.

CVE-2026-32274 at a Glance

CVE Identifier CVE-2026-32274
GHSA Identifier GHSA-3936-cmfr-pm3m
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Affected Product Black
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2026-32274

To remediate this vulnerability, upgrade all affected Black dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

black fixed: 26.3.1 
pip install black>=26.3.1
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show black

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-32274, inspect your installed packages using pip:

pip show black

Analyze the terminal output to locate any version of Black in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 26.3.1), your application is affected.

Note: The pip show black command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'), where the product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. In Black, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### 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.

CVE-2026-32274 Affected Black Versions

1 component(s)
Fixed Versions:
26.3.1
Product / Package Ecosystem Affected Versions Fixed Version
black
pypi/black
PyPI
≥ 24.3.0
< 26.3.1
26.3.1

References

GitHub Advisory / Wiki ADVISORY
https://github.com/psf/black/security/advisories/GHSA-3936-cmfr-pm3m
NVD — CVE-2026-32274 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-32274
Black Source Repository REPOSITORY
https://github.com/psf/black/pull/4176
Black Source Repository REPOSITORY
https://github.com/psf/black/pull/5038
Security Fix Commit FIX COMMIT
https://github.com/psf/black/commit/4937fe6cf241139ddbfc16b0bdbb5b422798909d
Security Fix Commit FIX COMMIT
https://github.com/psf/black/commit/ed770ba4dd50c419148a0fca2b43937a7447e1f9
access.redhat.com/errata/rhsa-2026:10... WEB
https://access.redhat.com/errata/RHSA-2026:10184
access.redhat.com/errata/rhsa-2026:13... WEB
https://access.redhat.com/errata/RHSA-2026:13545
access.redhat.com/errata/rhsa-2026:13... WEB
https://access.redhat.com/errata/RHSA-2026:13553
Black Security Information SECURITY
https://access.redhat.com/security/cve/CVE-2026-32274
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=2447111
Black Source Repository REPOSITORY
https://github.com/psf/black
Black Release RELEASE
https://github.com/psf/black/releases/tag/26.3.1
Black Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/black/PYSEC-2026-2121.yaml
Black Security Information SECURITY
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-32274.json

Frequently Asked Questions

What is CVE-2026-32274?
CVE-2026-32274 is a security vulnerability in Black involving Arbitrary file writes from unsanitized user input in cache file name under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal').
Which Black versions are affected?
Affected versions include releases prior to 26.3.1 across affected packages: black.
What version fixes CVE-2026-32274?
Upgrading to 26.3.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is black affected?
Yes, black is affected in releases prior to 26.3.1. Upgrade your dependency to 26.3.1 or later.
What is the CVSS score of CVE-2026-32274?
CVE-2026-32274 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
What CWE is associated with CVE-2026-32274?
CVE-2026-32274 is classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') (The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.).
How can I check PyPI dependencies for CVE-2026-32274?
Run the dependency tree command: 'pip show black'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-3936-cmfr-pm3m",
  "modified" : "2026-08-03T20:35:16Z",
  "published" : "2026-03-12T18:33:10Z",
  "aliases" : [ "CVE-2026-32274" ],
  "summary" : "Black: Arbitrary file writes from unsanitized user input in cache file name",
  "details" : "### Impact\n\nBlack 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. \n\n### Patches\n\nFixed in Black 26.3.1.\n\n### Workarounds\n\nDo not allow untrusted user input into the value of the `--python-cell-magics` option.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "black"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "24.3.0"
      }, {
        "fixed" : "26.3.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/psf/black/security/advisories/GHSA-3936-cmfr-pm3m"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-32274"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/psf/black/pull/4176"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/psf/black/pull/5038"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/psf/black/commit/4937fe6cf241139ddbfc16b0bdbb5b422798909d"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/psf/black/commit/ed770ba4dd50c419148a0fca2b43937a7447e1f9"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:10184"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:13545"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:13553"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/security/cve/CVE-2026-32274"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2447111"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/psf/black"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/psf/black/releases/tag/26.3.1"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/black/PYSEC-2026-2121.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-32274.json"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-12T18:33:10Z",
    "nvd_published_at" : "2026-03-12T20:16:06Z"
  }
}