#VU45820 Reachable Assertion in ISC BIND - CVE-2020-8621

Vulnerability identifier: #VU45820

Vulnerability risk: Medium

CVSSv4.0: 6.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2020-8621

CWE-ID: CWE-617

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
ISC BIND
Server applications / DNS servers

Vendor: ISC

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to a reachable assertion in resolver.c while attempting QNAME minimization after forwarding. If a server is configured with both QNAME minimization and 'forward first' then an attacker who can send queries to it may be able to trigger the condition that will cause the server to crash.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

ISC BIND: 9.14.0 rc1 - 9.17.3

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External links
https://kb.isc.org/docs/cve-2020-8621

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.