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ISC BIND 9 CVE-2026-5950

| EUVD-2026-31109 MEDIUM
Unchecked Input for Loop Condition (CWE-606)
2026-05-20 isc GHSA-2pjm-rchf-gxmp
5.3
CVSS 3.1
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CVSS VectorNVD

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low

Lifecycle Timeline

1
Analysis Generated
May 20, 2026 - 13:36 vuln.today

DescriptionNVD

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.

AnalysisAI

Resource exhaustion in ISC BIND 9's resolver state machine allows remote unauthenticated attackers to trigger an unbounded resend loop by sending crafted DNS queries that activate bad-server retry conditions, degrading resolver availability. Multiple active release branches are affected across standard and Subscription Edition builds spanning versions 9.18.36 through 9.21.21. …

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Vendor StatusVendor

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CVE-2026-5950 vulnerability details – vuln.today

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