Bleach LIB Style Attr ReDoS via bleach.clean
CVE-2020-6817 Published on February 16, 2023
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']}).
Vulnerability Analysis
CVE-2020-6817 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. An automatable proof of concept (POC) exploit exists. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.
Weakness Type
What is a ReDoS Vulnerability?
The product uses a regular expression with an inefficient, possibly exponential worst-case computational complexity that consumes excessive CPU cycles. Some regular expression engines have a feature called "backtracking". If the token cannot match, the engine "backtracks" to a position that may result in a different token that can match. Backtracking becomes a weakness if all of these conditions are met:
CVE-2020-6817 has been classified to as a ReDoS vulnerability or weakness.
Products Associated with CVE-2020-6817
stack.watch emails you whenever new vulnerabilities are published in Mozilla Bleach or Canonical Ubuntu Linux. Just hit a watch button to start following.
Affected Versions
Mozilla Bleach:- Version unspecified and below 3.1.4 is affected.
Vulnerable Packages
The following package name and versions may be associated with CVE-2020-6817
| Package Manager | Vulnerable Package | Versions | Fixed In |
|---|---|---|---|
| pip | bleach | < 3.1.4 | 3.1.4 |
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.