Affected: ISC BIND9

A malicious actor who intentionally exploits this lack of effective limitation on the number of fetches performed when processing referrals can, through the use of specially crafted referrals, cause a recursing server to issue a very large number of fetches in an attempt to process the referral. This has at least two potential effects: The performance of the recursing server can potentially be degraded by the additional work required to perform these fetches, and The attacker can exploit this behavior to use the recursing server as a reflector in a reflection attack with a high amplification factor.

Affected: Ubuntu:16.04:LTS: bind9, Ubuntu:18.04:LTS: bind9, Ubuntu:20.04:LTS: bind9

Lior Shafir, Yehuda Afek, and Anat Bremler-Barr discovered that Bind incorrectly limited certain fetches. A remote attacker could possibly use this issue to cause Bind to consume resources, leading to a denial of service, or possibly use Bind to perform a reflection attack. (CVE-2020-8616)

Tobias Klein discovered that Bind incorrectly handled checking TSIG validity. A remote attacker could use this issue to cause Bind to crash, resulting in a denial of service, or possibly perform other attacks. (CVE-2020-8617)