CVE-2020-6817
bleach.clean behavior parsing style attributes could result in a regular expression denial of service (ReDoS).
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.72%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
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']}).
- CVSS 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 0.72% probability · 54th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-1333
- Affected
- mozilla/bleach
- Source
- security@mozilla.org
EPSS 0.7% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=1623633Exploit, Issue Tracking
- https://github.com/mozilla/bleach/security/advisories/GHSA-vqhp-cxgc-6wmmVendor Advisory
- https://bugzilla.mozilla.org/show_bug.cgi?id=1623633Exploit, Issue Tracking
- https://github.com/mozilla/bleach/security/advisories/GHSA-vqhp-cxgc-6wmmVendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.