Versions of the package black before 24.3.0 are vulnerable to Regular Expression Denial of Service (ReDoS) via the lines_with_leading_tabs_expanded function in the strings.py file. An attacker could exploit this vulnerability by crafting a malicious input that causes a denial of service.

Exploiting this vulnerability is possible when running Black on untrusted input, or if you habitually put thousands of leading tab characters in your docstrings.

References

• https://nvd.nist.gov/vuln/detail/CVE-2024-21503
• psf/black@f000936
• https://github.com/psf/black/releases/tag/24.3.0
• https://security.snyk.io/vuln/SNYK-PYTHON-BLACK-6256273
• https://github.com/pypa/advisory-database/tree/main/vulns/black/PYSEC-2024-48.yaml