[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
black (changelog)	26.10.0 → 26.10.1

---

Black: GitHub Action installs unvalidated required-version from pyproject.toml

CVE-2026-114134 / GHSA-cg8m-r9f2-5wm2

More information

Details

Summary

The GitHub Action bundled with Black can read the version from tool.black.required-version if use_pyproject is set to True. This version is not validated and therefore can be used to execute untrusted code in the context of a victim's repository.

Details

This is similar to the previous CVE-2026-31900. The value in tool.black.required-version is accepted as the version to be installed by the action without validation.

Proof of concept

Reproduction requires a victim to use Black's GitHub Action with use_pyproject: true. The attacker would then issue a PR to the victim's repository with pyproject.toml edited so that Black points to a malicious repository.

Impact

This is a remote code execution vulnerability impacting users using the GitHub Action bundled with psf/black and using the use_pyproject: true setting.

Severity

• CVSS Score: 8.7 / 10 (High)
• Vector String: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

References

• https://github.com/psf/black/security/advisories/GHSA-cg8m-r9f2-5wm2
• https://github.com/psf/black/pull/5510
• https://github.com/psf/black/commit/ac1f71563aeccf73cf13ece00f231d9d6c66a514
• https://github.com/psf/black/releases/tag/26.10.1
• https://github.com/advisories/GHSA-cg8m-r9f2-5wm2

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Release Notes

psf/black (black)

v26.10.1

Compare Source

Highlights

This release fixes a security issue in Black's bundled GitHub Action. Repositories that
use the action are encouraged to update to the latest version of Black immediately. This
update is received automatically when using psf/black@stable, and is independent of
the version of Black installed by the action.

When the GitHub Action reads version specifiers from tool.black.required-version, it
now only accepts released versions of Black, as it already did for black requirements
in dependency lists. Other values, such as URL references, are now rejected. This issue
has been registered as GHSA-cg8m-r9f2-5wm2; a CVE identifier is pending.

Stable style

• Fix a long Jupyter notebook assignment magic (for example x = !ls -la) being wrapped
  in parentheses, which IPython can no longer run; such cells are now left unchanged
  (#​5481)
• Keep repeated lines outside the selected --line-ranges unchanged (#​5436)
• Fix --line-ranges formatting lines that follow a statement when formatting joins or
  re-indents that statement (#​5484)
• Fix --line-ranges crashing with an internal error when an unselected statement has a
  # fmt: skip comment on the last line before a closing bracket (#​5477)
• Prevent moving an encoding declaration (for example # -*- coding: latin-1 -*-) onto
  the first two lines of a file (#​5487)
• Fix adding an extra trailing blank line inside a multi-line module docstring when its
  last line is near the line length limit (#​5494)
• Keep the parentheses around a walrus that is the only item in a set (for example
  {(x := f())}) when targeting Python 3.9 or older, since Python 3.8 and 3.9.0 can't
  parse it without them (#​5502)

Preview style

• Do not split short expressions on delimiters (such as binary operators, comparisons,
  or comprehensions) inside brackets when preceded by a standalone comment (#​5455)
• Fix the unstable string_processing feature removing backslash-newline sequences from
  raw strings, which changed their value (#​5482)
• Avoid adding unnecessary parentheses around unbreakable right-hand side expressions in
  assignments (such as annotated assignments or subscript targets) (#​5473)
• Parenthesize expressions with parameter comments when they exceed the line length
  under --preview (#​5442)
• Fix wrap_long_dict_values_in_parens dropping the parentheses around a right-hand
  side that contains a dictionary, leaving a line over the length limit (#​5492)
• Fix the unstable string_processing feature adding a space after * or ** in a PEP
  695 type parameter (* Ts = ...) when it splits a string in the parameter's default
  (#​5504)
• Avoid unnecessary line splits of trailers (such as indexing/subscripts) when an
  earlier bracket split exceeds the line length only due to a trailing comment (#​5498)

Configuration

• Add --cache-dir to configure the cache directory from the command line (#​5433)
• Don't cache a file as formatted after formatting or checking it with --line-ranges,
  which made a later full black --check pass and black skip the unformatted lines
  (#​5476)
• Respect a .gitignore that starts with a UTF-8 byte order mark. The mark became part
  of the first pattern, so that pattern never matched and Black formatted files that git
  ignores (#​5497)

Performance

• Avoid quadratic runtime when splitting very long lines with many trailing bracket
  pairs (such as consecutive subscripts) (#​5475)

Integrations

• Fix the GitHub Action crashing on dependency-group includes when use_pyproject is
  enabled (#​5479)
• When the GitHub Action reads version specifiers from tool.black.required-version, it
  now only accepts released versions of Black, as it already did for black
  requirements in dependency lists. Other values, such as URL references, are now
  rejected. (#​5510)

---

Configuration

📅 Schedule: (in timezone Europe/Warsaw)

• Branch creation
  • At any time (no schedule defined)
• Automerge
  • At any time (no schedule defined)

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever PR is behind base branch, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

---

• If you want to rebase/retry this PR, check this box

---

This PR was generated by Mend Renovate. View the repository job log.