CVE-2020-6817
regular expression denial-of-service (ReDoS) in Bleach
Impact
### 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
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| pip | bleach | < 3.1.4 | 3.1.4 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Mozilla | Bleach | before 3.1.4 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://bugzilla.mozilla.org/show_bug.cgi?id=1623633
- https://github.com/mozilla/bleach/security/advisories/GHSA-vqhp-cxgc-6wmm
- https://github.com/advisories/GHSA-vqhp-cxgc-6wmm
- https://github.com/mozilla/bleach/releases/tag/v3.1.4
- https://nvd.nist.gov/vuln/detail/CVE-2020-6817
- https://snyk.io/vuln/SNYK-PYTHON-BLEACH-561754
- https://github.com/pypa/advisory-database/tree/main/vulns/bleach/PYSEC-2020-340.yaml