BIND 9 Unbounded Resend Loop Causing Resource Exhaustion (9.18.369.18.48)
CVE-2026-5950 Published on May 20, 2026
Unbounded resend loop in BIND 9 resolver
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.
Vulnerability Analysis
CVE-2026-5950 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a small impact on availability.
Weakness Type
Unchecked Input for Loop Condition
The product does not properly check inputs that are used for loop conditions, potentially leading to a denial of service or other consequences because of excessive looping.
Products Associated with CVE-2026-5950
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Affected Versions
ISC BIND 9:- Version 9.18.36, <= 9.18.48 is affected.
- Version 9.20.8, <= 9.20.22 is affected.
- Version 9.21.7, <= 9.21.21 is affected.
- Version 9.18.36-S1, <= 9.18.48-S1 is affected.
- Version 9.20.9-S1, <= 9.20.22-S1 is affected.