Affected: ISC BIND 9

An unbounded resend loop vulnerability exists in the BIND 9 resolver state machine during bad-server handling, enabling a remote unauthenticated attacker to cause severe resource exhaustion by sending queries that trigger specific retry conditions. This issue affects BIND 9 versions 9.18.36 through 9.18.48, 9.20.8 through 9.20.22, 9.21.7 through 9.21.21, 9.18.36-S1 through 9.18.48-S1, and 9.20.9-S1 through 9.20.22-S1.

Affected: Ubuntu:22.04:LTS: bind9, Ubuntu:24.04:LTS: bind9, Ubuntu:25.10: bind9, Ubuntu:26.04:LTS: bind9

Vitaly Simonovich discovered that Bind could exhaust memory during GSS-API TKEY negotiation. A remote attacker could possibly use this issue to cause Bind to use excessive resources, leading to a denial of service. (CVE-2026-3039)

Shuhan Zhang discovered that Bind incorrectly handled self-pointed glue records. A remote attacker could possibly use this issue to use Bind in denial of service amplification attacks against other systems. (CVE-2026-3592)

Naresh Kandula Parmar discovered that Bind incorrectly handled memory in the DNS-over-HTTPS implementation. A remote attacker could possibly use this issue to cause Bind to crash, resulting in a denial of service, or execute arbitrary code. This issue only affected Ubuntu 25.10 and Ubuntu 26.04 LTS. (CVE-2026-3593)

It was discovered that Bind incorrectly handled DNS messages whose class was not IN. A remote attacker could possibly use this issue to cause Bind to crash, resulting in a denial of service. (CVE-2026-5946)

Naoki Wakamatsu discovered that Bind incorrectly handled SIG(0) validation during a query flood. A remote attacker could possibly use this issue to cause Bind to crash, resulting in a denial of service. This issue only affected Ubuntu 25.10 and Ubuntu 26.04 LTS. (CVE-2026-5947)

Billy Baraja discovered that Bind had an unbounded resend loop in the resolver. A remote attacker could possibly use this issue to cause Bind to use excessive resources, leading to a denial of service. (CVE-2026-5950)