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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.
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Title: BIND 9 de ISC, Description: Una vulnerabilidad de bucle de reenvío ilimitado existe en la máquina de estados del resolvedor de BIND 9 durante el manejo de servidores defectuosos, permitiendo a un atacante remoto no autenticado causar un agotamiento severo de recursos enviando consultas que activan condiciones de reintento específicas.
Este problema afecta a las versiones de BIND 9 9.18.36 a 9.18.48, 9.20.8 a 9.20.22, 9.21.7 a 9.21.21, 9.18.36-S1 a 9.18.48-S1, y 9.20.9-S1 a 9.20.22-S1.
OR
*cpe:2.3:a:isc:bind:*:*:*:*:-:*:*:* versions from (including) 9.18.36 up to (excluding) 9.18.49
*cpe:2.3:a:isc:bind:*:*:*:*:-:*:*:* versions from (including) 9.20.8 up to (excluding) 9.20.23
*cpe:2.3:a:isc:bind:*:*:*:*:-:*:*:* versions from (including) 9.21.7 up to (excluding) 9.21.21
Added
Reference Type
Internet Systems Consortium (ISC): https://downloads.isc.org/isc/bind9/9.18.49 Types: Patch
Added
Reference Type
Internet Systems Consortium (ISC): https://downloads.isc.org/isc/bind9/9.20.23 Types: Patch
Added
Reference Type
Internet Systems Consortium (ISC): https://downloads.isc.org/isc/bind9/9.21.22 Types: Patch
Added
Reference Type
Internet Systems Consortium (ISC): https://kb.isc.org/docs/cve-2026-5950 Types: Vendor Advisory
New CVE Received from Internet Systems Consortium (ISC)5/20/2026 9:16:40 AM
Action
Type
Old Value
New Value
Added
Description
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.
Added
CVSS V3.1
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Added
CWE
CWE-606
Added
Reference
https://downloads.isc.org/isc/bind9/9.18.49
Added
Reference
https://downloads.isc.org/isc/bind9/9.20.23
Added
Reference
https://downloads.isc.org/isc/bind9/9.21.22
Added
Reference
https://kb.isc.org/docs/cve-2026-5950
Quick Info
CVE Dictionary Entry: CVE-2026-5950 NVD
Published Date: 05/20/2026 NVD
Last Modified: 07/23/2026
Source: Internet Systems Consortium (ISC)