CVE-2020-8617 : Vulnerability Insights and Analysis

A logic error in code which checks TSIG validity can be used to trigger an assertion failure in tsig.c.

Understanding CVE-2020-8617

This CVE involves a vulnerability in BIND9 that could allow an attacker to cause a denial of service by triggering an assertion failure in tsig.c.

What is CVE-2020-8617?

An attacker can exploit a logic error in BIND code to cause a server to reach an inconsistent state by manipulating a specially-crafted message.
The vulnerability affects various versions of BIND, making almost all current BIND servers vulnerable.

The Impact of CVE-2020-8617

CVSS Base Score: 7.5 (High)
Attack Vector: Network
Availability Impact: High
No Confidentiality or Integrity Impact
No Privileges Required
Scope: Unchanged
No User Interaction Required

Technical Details of CVE-2020-8617

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

Vulnerability Description

The vulnerability arises from an error in BIND code that checks the validity of messages containing TSIG resource records.
Exploiting this error can lead to an assertion failure in tsig.c, resulting in denial of service to clients.

Affected Systems and Versions

Products: BIND9
Vendor: ISC
Versions: 9.0.0 -> 9.11.18, 9.12.0 -> 9.12.4-P2, 9.14.0 -> 9.14.11, 9.16.0 -> 9.16.2, and releases 9.17.0 -> 9.17.1 of the 9.17 experimental development branch.

Exploitation Mechanism

An attacker can exploit this vulnerability by sending a specially-crafted message to the BIND server, manipulating the TSIG key.

Mitigation and Prevention

Protecting systems from CVE-2020-8617 involves taking immediate steps and implementing long-term security practices.

Immediate Steps to Take

Upgrade to the patched release most closely related to your current version of BIND: BIND 9.11.19, BIND 9.14.12, BIND 9.16.3.

Long-Term Security Practices

Regularly update BIND to the latest version to ensure all security patches are applied.
Monitor security advisories from vendors and security communities for any new vulnerabilities.

Patching and Updates

Ensure that BIND Supported Preview Edition is updated to BIND 9.11.19-S1.