CVE-2021-25218 : Security Advisory and Response

A deep dive into the BIND vulnerability affecting versions 9.16.19, 9.17.16, and 9.16.19-S1 that could lead to a server process termination.

Understanding CVE-2021-25218

This CVE involves a too-strict assertion check in BIND versions 9.16.19 and 9.17.16 when UDP fragmentation is required, potentially causing server crashes.

What is CVE-2021-25218?

BIND 9 releases 9.16.19, 9.17.16, and Supported Preview Edition 9.16.19-S1 are vulnerable to assertion failures, leading to named process termination.

The Impact of CVE-2021-25218

The vulnerability can cause the named process to halt when receiving specific queries under the described circumstances, affecting BIND's stability.

Technical Details of CVE-2021-25218

Get insights into the vulnerability, its affected systems, and how exploitation can occur.

Vulnerability Description

An assertion failure in named occurs when attempting to respond over UDP with a larger-than-MTU response under active response-rate limiting (RRL).

Affected Systems and Versions

BIND 9.16.19, 9.17.16, and Supported Preview Edition 9.16.19-S1 are impacted by this flaw.

Exploitation Mechanism

The vulnerability can be triggered through misconfiguration or deliberate exploitation, affecting server processes.

Mitigation and Prevention

Learn how to address and prevent the CVE-2021-25218 vulnerability efficiently.

Immediate Steps to Take

Disabling RRL and applying specific configurations in named.conf can prevent the assertion failure.

Long-Term Security Practices

Regularly update BIND to the patched releases like BIND 9.16.20 and BIND 9.17.17 to mitigate security risks.

Patching and Updates

Ensure systems are up-to-date with the latest BIND versions, including BIND Supported Preview Edition 9.16.20-S1.