GHSA-vqhp-cxgc-6wmm regular expression denial-of-service (ReDoS) in Bleach

• PyPI bleach: < 3.1.4 → fixed in 3.1.4

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 [email protected]