CVE-2021-40083 : Security Advisory and Response

Knot Resolver before 5.3.2 is prone to an assertion failure, triggerable by a remote attacker in an edge case (NSEC3 with too many iterations used for a positive wildcard proof).

Understanding CVE-2021-40083

This CVE pertains to a vulnerability in Knot Resolver prior to version 5.3.2 that can lead to an assertion failure when a remote attacker exploits a specific edge case.

What is CVE-2021-40083?

CVE-2021-40083 highlights a flaw in Knot Resolver, where an attacker can trigger an assertion failure by manipulating NSEC3 with excessive iterations for a positive wildcard proof.

The Impact of CVE-2021-40083

The vulnerability could be exploited by a remote attacker to cause an assertion failure in Knot Resolver, potentially leading to a denial of service (DoS) condition.

Technical Details of CVE-2021-40083

This section delves into the specifics of the CVE to better understand its implications.

Vulnerability Description

The flaw in Knot Resolver before version 5.3.2 allows a remote attacker to cause an assertion failure by using NSEC3 with an excessive number of iterations for a positive wildcard proof.

Affected Systems and Versions

Affected Systems: Not applicable
Affected Versions: Knot Resolver versions prior to 5.3.2

Exploitation Mechanism

The vulnerability can be exploited by a remote attacker who can manipulate the NSEC3 functionality with an unusually high number of iterations.

Mitigation and Prevention

To mitigate the risks associated with CVE-2021-40083, the following steps are recommended:

Immediate Steps to Take

Upgrade Knot Resolver to version 5.3.2 or newer to eliminate the vulnerability.
Monitor for any unusual activities on the network that might indicate exploitation.

Long-Term Security Practices

Regularly update and patch all software components to prevent known vulnerabilities.
Implement network segmentation and access controls to limit the impact of potential attacks.

Patching and Updates

Ensure timely application of security patches and updates to all relevant systems and software components to address vulnerabilities like CVE-2021-40083.