#VU28123 Reachable Assertion in ISC BIND - CVE-2020-8617

Vulnerability identifier: #VU28123

Vulnerability risk: Medium

CVSSv4.0: 8.7 [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:A/U:Green]

CVE-ID: CVE-2020-8617

CWE-ID: CWE-617

Exploitation vector: Network

Exploit availability: Yes

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 when checking validity of messages containing TSIG resource records within tsig.c. A remote attacker can send a specially crafted message and 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.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

ISC BIND: 9.0.0 rc1 - 9.17.1

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External links
https://kb.isc.org/docs/cve-2020-8617
https://www.openwall.com/lists/oss-security/2020/05/19/4

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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. However, a fully functional exploit for this vulnerability is available.