CVE-2020-6817 – bleach

Package

Manager: pip
Name: bleach
Vulnerable Version: >=0 <3.1.4

Severity

Level: High

CVSS v3.1: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

EPSS: 0.00167 pctl0.38267

Details

regular expression denial-of-service (ReDoS) in Bleach ### Impact `bleach.clean` behavior parsing style attributes could result in a regular expression denial of service (ReDoS). Calls to ``bleach.clean`` with an allowed tag with an allowed ``style`` attribute are vulnerable to ReDoS. For example, ``bleach.clean(..., attributes={'a': ['style']})``. ### Patches 3.1.4 ### Workarounds * do not whitelist the style attribute in `bleach.clean` calls * limit input string length ### References * https://bugzilla.mozilla.org/show_bug.cgi?id=1623633 * https://www.regular-expressions.info/redos.html * https://blog.r2c.dev/posts/finding-python-redos-bugs-at-scale-using-dlint-and-r2c/ * https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-6817 ### Credits * Reported by schwag09 of r2c ### For more information If you have any questions or comments about this advisory: * Open an issue at https://github.com/mozilla/bleach/issues * Email us at security@mozilla.org

Metadata

Created: 2020-03-30T19:45:56Z
Modified: 2025-03-20T18:49:18Z
Source: https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2020/03/GHSA-vqhp-cxgc-6wmm/GHSA-vqhp-cxgc-6wmm.json
CWE IDs: ["CWE-1333", "CWE-400"]
Alternative ID: GHSA-vqhp-cxgc-6wmm
Finding: F211
Auto approve: 1