CVE-2020-8617 - Reachable Assertion

Severity

75%

Complexity

39%

Confidentiality

60%

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.

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.

CVSS 3.1 Base Score 7.5. CVSS Attack Vector: network. CVSS Attack Complexity: low. CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

CVSS 2.0 Base Score 5. CVSS Attack Vector: network. CVSS Attack Complexity: low. CVSS Vector: (AV:N/AC:L/Au:N/C:N/I:N/A:P).

Demo Examples

Reachable Assertion

CWE-617

In the excerpt below, an AssertionError (an unchecked exception) is thrown if the user hasn't entered an email address in an HTML form.


               
assert email != null;

Overview

First reported 4 years ago

2020-05-19 14:15:00

Last updated 4 years ago

2020-10-20 12:15:00

Affected Software

ISC BIND

ISC BIND 9.12.4 Patch 1

9.12.4

ISC BIND 9.9.3 S1 Supported Preview Edition

9.9.3

ISC BIND 9.10.5 S1 Supported Preview Edition

9.10.5

ISC BIND 9.10.7 S1 Supported Preview Edition

9.10.7

ISC BIND 9.11.3 S1 Supported Preview Edition

9.11.3

ISC BIND 9.11.5 S3 Supported Preview Edition

9.11.5

ISC BIND 9.11.5 S5 Supported Preview Edition

9.11.5

ISC BIND 9.11.6 S1 Supported Preview Edition

9.11.6

ISC BIND 9.11.7 S1 Supported Preview Edition

9.11.7

Debian Linux 9.0

9.0

Debian Linux 10

10

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