# CVE-2024-21503: black: Versions of the package black before 24.3.0 are vulnerable to Regular Expression Denial of Service (ReDoS) via the li...

CVE-2024-21503 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2024-21503, released March 19, 2024. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2024-21503
- Priority: Routine
- CVSS: 5.3 (medium)
- EPSS: 0.0098
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Mar 19, 2024

## Description

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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | black Debian 13.5 (trixie) | 24.4.0-1 | [DEBIAN-CVE-2024-21503](https://patchblox.com/security/data/fix/linux/debian-cve-2024-21503.md) | Mar 19, 2024 |
| Linux | black Debian 14 | 24.4.0-1 | [DEBIAN-CVE-2024-21503](https://patchblox.com/security/data/fix/linux/debian-cve-2024-21503.md) | Mar 19, 2024 |
| Linux | python-black opensuse-leap 15.6 | 24.3.0-150400.9.8.1 | [SUSE-SU-2024:2481-1](https://patchblox.com/security/data/fix/linux/suse-su-2024-2481-1.md) | Jul 15, 2024 |

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Data as of 2026-11-10T01:44:33Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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