CVE-2019-16201 Explained : Impact and Mitigation

CVE-2019-16201 is a regular expression Denial of Service vulnerability in the WEBrick::HTTPAuth::DigestAuth library in Ruby versions 2.4.7, 2.5.x up to 2.5.6, and 2.6.x up to 2.6.4. This vulnerability is caused by looping/backtracking, requiring a WEBrick server using DigestAuth to be exposed to an untrusted network or the internet.

Understanding CVE-2019-16201

This CVE identifies a specific vulnerability in Ruby versions that can lead to a Denial of Service attack.

What is CVE-2019-16201?

The vulnerability in the WEBrick::HTTPAuth::DigestAuth library in certain Ruby versions can be exploited by attackers to cause a Denial of Service by triggering looping/backtracking.

The Impact of CVE-2019-16201

The vulnerability can result in a Denial of Service attack on systems utilizing affected Ruby versions, potentially disrupting services and causing system unavailability.

Technical Details of CVE-2019-16201

This section provides more in-depth technical information about the CVE.

Vulnerability Description

The vulnerability arises from a flaw in the regular expression handling within the WEBrick::HTTPAuth::DigestAuth library, leading to a potential Denial of Service condition.

Affected Systems and Versions

Ruby 2.4.7
Ruby 2.5.x up to 2.5.6
Ruby 2.6.x up to 2.6.4

Exploitation Mechanism

To exploit this vulnerability, an attacker needs to target a WEBrick server that is using DigestAuth and is accessible from an untrusted network or the internet.

Mitigation and Prevention

Protecting systems from CVE-2019-16201 involves immediate actions and long-term security practices.

Immediate Steps to Take

Update Ruby to a patched version that addresses the vulnerability.
Restrict network access to the WEBrick server to trusted sources only.

Long-Term Security Practices

Regularly monitor and apply security updates for all software components.
Implement network segmentation to limit exposure of critical services.

Patching and Updates

Ensure that Ruby versions 2.4.8, 2.5.7, and 2.6.5 or later are installed to mitigate the vulnerability.