CVE-2023-34104 : Exploit Details and Defense Strategies

fast-xml-parser is an open-source, pure JavaScript XML parser. A vulnerability known as Regex Injection via Doctype Entities has been identified in versions >= 4.1.3 and < 4.2.4 of fast-xml-parser. This CVE allows special characters in entity names that are not escaped or sanitized, leading to a potential denial of service (DoS) attack. Attackers can exploit this by crafting malicious entity names, causing the parser to stall indefinitely. This issue has been patched in version 4.2.4, and users are strongly advised to update their installations to mitigate this vulnerability.

Understanding CVE-2023-34104

This section sheds light on the technical aspects of CVE-2023-34104:

What is CVE-2023-34104?

CVE-2023-34104 involves Regex Injection via Doctype Entities in the fast-xml-parser, enabling attackers to execute DoS attacks by utilizing specially crafted entity names. The vulnerability arises from unescaped special characters in entity names used for regex creation in the XML parser.

The Impact of CVE-2023-34104

The impact of this CVE is rated as high, with a CVSS base score of 7.5. Although confidentiality and integrity impacts are rated as none, the availability impact is significant. This vulnerability does not require any special privileges or user interaction, making it a relatively low-complexity threat.

Technical Details of CVE-2023-34104

Let's dive deeper into the technical specifics of CVE-2023-34104:

Vulnerability Description

fast-xml-parser allows unescaped special characters in entity names, potentially leading to DoS attacks. Crafting malicious entity names can result in a poorly performing regex, causing the parser to stall indefinitely.

Affected Systems and Versions

Versions >= 4.1.3 and < 4.2.4 of fast-xml-parser are affected by this vulnerability. Users with installations in this version range are at risk of exploitation.

Exploitation Mechanism

Attackers can exploit this vulnerability by creating malicious entity names with specially crafted characters that result in a slow-performing regex, thereby causing denial of service to the XML parser.

Mitigation and Prevention

To safeguard against CVE-2023-34104, consider the following mitigation strategies:

Immediate Steps to Take

Users are urged to update their fast-xml-parser installations to version 4.2.4, where this vulnerability has been addressed. Alternatively, users unable to update should disable DOCTYPE parsing by setting

processEntities: false

.

Long-Term Security Practices

Implement security best practices such as input validation, sanitization of user input, and regular security audits to identify and address vulnerabilities proactively.

Patching and Updates

Regularly monitor for security patches and updates from the maintainers of fast-xml-parser and promptly apply them to keep your systems secure.