Certain DNSSEC aspects of the DNS protocol (in RFC 4033, 4034, 4035, 6840, and related RFCs) allow remote attackers to cause a denial of service (CPU consumption) via one or more DNSSEC responses, aka the "KeyTrap" issue. One of the concerns is that, when there is a zone with many DNSKEY and RRSIG records, the protocol specification implies that an algorithm must evaluate all combinations of DNSKEY and RRSIG records.

Affected: Ubuntu:22.04:LTS: bind9

Shoham Danino, Anat Bremler-Barr, Yehuda Afek, and Yuval Shavitt discovered that Bind incorrectly handled parsing large DNS messages. A remote attacker could possibly use this issue to cause Bind to consume resources, leading to a denial of service. (CVE-2023-4408)

Elias Heftrig, Haya Schulmann, Niklas Vogel, and Michael Waidner discovered that Bind icorrectly handled validating DNSSEC messages. A remote attacker could possibly use this issue to cause Bind to consume resources, leading to a denial of service. (CVE-2023-50387)

It was discovered that Bind incorrectly handled preparing an NSEC3 closest encloser proof. A remote attacker could possibly use this issue to cause Bind to consume resources, leading to a denial of service. (CVE-2023-50868)

It was discovered that Bind incorrectly handled reverse zone queries when nxdomain-redirect is enabled. A remote attacker could possibly use this issue to cause Bind to crash, leading to a denial of service. (CVE-2023-5517)

It was discovered that Bind incorrectly handled recursive resolution when both DNS64 and serve-stable were enabled. A remote attacker could possibly use this issue to cause Bind to crash, leading to a denial of service. (CVE-2023-5679)