CVE-2026-5950
Denial of Service in BIND 9 Resolver
Publication date: 2026-05-20
Last updated on: 2026-05-20
Assigner: Internet Systems Consortium (ISC)
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| isc | bind | From 9.18.36 (inc) to 9.18.48 (inc) |
| isc | bind | From 9.20.8 (inc) to 9.20.22 (inc) |
| isc | bind | From 9.21.7 (inc) to 9.21.21 (inc) |
| isc | bind | From 9.20.9 (inc) to 9.20.22 (inc) |
| isc | bind | 9.18 |
| isc | bind | 9.20 |
| isc | bind | 9.21 |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-606 | 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. |
Attack-Flow Graph
AI Powered Q&A
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
The provided information does not specify any direct impact of this vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.
Can you explain this vulnerability to me?
CVE-2026-5950 is a vulnerability in the BIND 9 DNS resolver where an unbounded resend loop occurs in the resolver's state machine during bad-server handling.
This happens when queries trigger specific retry conditions, allowing a remote unauthenticated attacker to cause the resolver to repeatedly resend queries without limit.
As a result, this leads to severe resource exhaustion on the affected system.
How can this vulnerability impact me? :
The vulnerability can cause severe resource exhaustion on systems running vulnerable versions of the BIND 9 resolver.
This resource exhaustion could degrade system performance or availability, potentially leading to denial of service conditions.
Since the attack can be performed remotely and without authentication, it poses a risk to any exposed resolver using affected BIND 9 versions.
What immediate steps should I take to mitigate this vulnerability?
The immediate step to mitigate this vulnerability is to upgrade BIND to a patched version.
- Upgrade to BIND 9.18.49, 9.20.23, or 9.21.22, or their Supported Preview Edition equivalents.
No known workarounds exist, so upgrading is the recommended and effective mitigation.