CVE-2019-6477 : Vulnerability Insights and Analysis

CVE-2019-6477 addresses a vulnerability in BIND9 that allows TCP-pipelined queries to bypass the tcp-clients limit, potentially causing server overload and unresponsiveness.

Understanding CVE-2019-6477

What is CVE-2019-6477?

When utilizing TCP-pipelined connections, a server may become overwhelmed by the release of resources upon closing connections, leading to unresponsiveness and potential service degradation.

The Impact of CVE-2019-6477

CVSS Base Score: 7.5 (High)
Attack Vector: Network
Availability Impact: High
Attack Complexity: Low
The vulnerability can cause servers to become unresponsive, affecting query responses and server performance.

Technical Details of CVE-2019-6477

Vulnerability Description

TCP-pipelined queries can bypass the tcp-clients limit, potentially causing server overload and unresponsiveness.

Affected Systems and Versions

Affected versions include BIND 9.11.6-P1 -> 9.11.12, 9.12.4-P1 -> 9.12.4-P2, 9.14.1 -> 9.14.7, and versions 9.11.5-S6 -> 9.11.12-S1 of BIND 9 Supported Preview Edition.

Exploitation Mechanism

By sending a large number of DNS requests over a single connection, a TCP client can bypass the new TCP clients limit, causing server overload.

Mitigation and Prevention

Immediate Steps to Take

Upgrade to patched releases like BIND 9.11.13, 9.14.8, or 9.15.6 to address the vulnerability.
Disabling TCP-pipelining can effectively mitigate the issue with minimal impact on clients.

Long-Term Security Practices

Regularly update BIND to the latest patched versions to prevent vulnerabilities.

Patching and Updates

Ensure BIND is updated to the latest version to address security issues.