CVE-2020-8617: A logic error in code which checks TSIG validity can be used to trigger an assertion failure in tsig.c

Vulnerability summary

CVE-2020-8617 is a high (CVSS 7.5) Reachable Assertion vulnerability in canonical ubuntu_linux. EPSS estimates a 93.33% chance of exploitation in the next 30 days, higher than 99.8% of scored vulnerabilities. 2 public exploits are recorded.

Timeline

1. 19-05-2020
   PublishedVulnerability first disclosed.
2. 16-09-2024
   Last modifiedVulnerability information updated.

Description

Using a specially-crafted message, an attacker may potentially cause a BIND server to reach an inconsistent state if the attacker knows (or successfully guesses) the name of a TSIG key used by the server. Since BIND, by default, configures a local session key even on servers whose configuration does not otherwise make use of it, almost all current BIND servers are vulnerable. In releases of BIND dating from March 2018 and after, an assertion check in tsig.c detects this inconsistent state and deliberately exits. Prior to the introduction of the check the server would continue operating in an inconsistent state, with potentially harmful results.

• CWE-617Reachable AssertionThe product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.