CVE-2026-5950: ISC BIND

Medium severity, CVSS 5.3. EPSS: 0.8% chance of exploitation in the next 30 days.

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 products

• ISC BIND: from 9.18.36, before 9.18.49 (fixed in 9.18.49); from 9.20.8, before 9.20.23 (fixed in 9.20.23); from 9.21.7, before 9.21.21 (fixed in 9.21.21)

Published 2026-05-20. Last modified 2026-07-23.