CVE-2021-44686 Explained : Impact and Mitigation

Calibre before 5.32.0 is susceptible to a Regular Expression Denial of Service (ReDoS) vulnerability in html_preprocess_rules.

Understanding CVE-2021-44686

This CVE involves a vulnerability in Calibre version 5.32.0 that can lead to a ReDoS attack.

What is CVE-2021-44686?

Calibre version 5.32.0 has a vulnerable regular expression in html_preprocess_rules in ebooks/conversion/preprocess.py.

The Impact of CVE-2021-44686

The vulnerability in Calibre before 5.32.0 can be exploited to cause a Regular Expression Denial of Service (ReDoS) attack.

Technical Details of CVE-2021-44686

This section delves into the technical aspects of the CVE.

Vulnerability Description

Calibre before 5.32.0 contains a regular expression that is prone to ReDoS in html_preprocess_rules in ebooks/conversion/preprocess.py.

Affected Systems and Versions

Product: Calibre
Vendor: Calibre
Versions affected: Prior to 5.32.0

Exploitation Mechanism

The vulnerability can be exploited by providing specially crafted input to trigger the ReDoS vulnerability.

Mitigation and Prevention

It's essential to take immediate and long-term measures to mitigate the risk of this vulnerability.

Immediate Steps to Take

Update Calibre to version 5.32.0 or later to patch the vulnerability.
Monitor for any unusual activities on the system.

Long-Term Security Practices

Regularly update software and dependencies to the latest secure versions.
Conduct security assessments and audits regularly to identify and address vulnerabilities.
Implement proper input validation mechanisms to prevent similar issues.
Educate developers on secure coding practices.

Patching and Updates

Ensure timely application of security patches and updates to Calibre to prevent exploitation of this ReDoS vulnerability.