CVE-2021-43843 : Security Advisory and Response

CVE-2021-43843 involves an insufficient patch for Regular Expression Denial of Service (ReDoS) in jsx-slack v4.5.1, leading to a medium-severity vulnerability.

Understanding CVE-2021-43843

What is CVE-2021-43843?

CVE-2021-43843 pertains to jsx-slack, a package for constructing JSON objects for Slack block kit surfaces. The vulnerability in version 4.5.1 exposes the system to ReDoS attacks due to insufficient regular expression handling.

The Impact of CVE-2021-43843

CVSS Score: 5.3 (Medium)
Attack Complexity: Low
Privileges Required: None
Attackers can exploit the vulnerability by injecting JSX elements with multibyte characters into

<blockquote>

tags, causing excessive resource consumption.

Technical Details of CVE-2021-43843

Vulnerability Description

The vulnerability in jsx-slack v4.5.1 allows attackers to trigger ReDoS attacks by overwhelming the internal regular expression mechanism used for escaping characters.

Affected Systems and Versions

Affected Versions: < 4.5.2

Exploitation Mechanism

By inserting numerous JSX elements containing multibyte characters into

<blockquote>

tags, attackers can trigger catastrophic backtracking in the regular expression engine.

Mitigation and Prevention

Immediate Steps to Take

Update jsx-slack to version 4.5.2 or later to mitigate the vulnerability.
Avoid processing untrusted JSX elements within blockquote tags.

Long-Term Security Practices

Regularly review and update regular expression handling mechanisms within applications.

Patching and Updates

Install patches and updates provided by the jsx-slack maintainers to address the vulnerability.