BIND 9 Assertion Failure: CVE-2026-5946 Impacts DNS Handling
Multiple critical flaws, tracked as CVE-2026-5946, have been identified in named, the daemon for BIND 9. According to the National Vulnerability Database, these issues stem from improper handling of DNS messages not using the Internet (IN) class, such as CHAOS or HESIOD. Additionally, problems arise with DNS messages that specify meta-classes like ANY or NONE in the question section.
Specially crafted requests targeting code paths for recursion, dynamic updates (UPDATE), zone change notifications (NOTIFY), or processing of IN-specific record types in non-IN data can trigger assertion failures. This leads to named crashing. The National Vulnerability Database rates this with a CVSSv3.1 score of 7.5 (HIGH), indicating a significant availability risk.
The vulnerability impacts a wide range of BIND 9 versions: 9.11.0 through 9.16.50, 9.18.0 through 9.18.48, 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, and their corresponding 9.11.3-S1, 9.18.11-S1, and 9.20.9-S1 extended support editions. Defenders must prioritize patching to maintain DNS service availability against denial-of-service attacks.
What This Means For You
- If your organization relies on BIND 9, you are directly exposed to a denial-of-service risk. Attackers can crash your `named` service with specially crafted DNS queries. Identify all BIND 9 instances in your environment and apply the latest security patches immediately. This isn't theoretical; an assertion failure means your DNS resolver goes down, impacting all services that rely on it.
Related ATT&CK Techniques
🛡️ Detection Rules
3 rules · 6 SIEM formats3 detection rules auto-generated for this incident, mapped to MITRE ATT&CK. Sigma YAML is free — export to any SIEM format via the Intel Bot.
BIND 9 Assertion Failure due to Non-Internet CLASS DNS Query - CVE-2026-5946
title: BIND 9 Assertion Failure due to Non-Internet CLASS DNS Query - CVE-2026-5946
id: scw-2026-05-20-ai-1
status: experimental
level: high
description: |
Detects specially crafted DNS queries targeting BIND 9 that use non-Internet CLASS types (e.g., CHAOS, HESIOD) or meta-classes (ANY, NONE) in the question section. This specific pattern is indicative of an attempt to trigger the assertion failures described in CVE-2026-5946, potentially leading to a denial of service or further exploitation.
author: SCW Feed Engine (AI-generated)
date: 2026-05-20
references:
- https://shimiscyberworld.com/posts/nvd-CVE-2026-5946/
tags:
- attack.initial_access
- attack.t1190
logsource:
category: dns
detection:
selection:
query|contains:
- 'CHAOS'
- 'HESIOD'
- 'ANY'
- 'NONE'
condition: selection
falsepositives:
- Legitimate administrative activity
Source: Shimi's Cyber World · License & reuse
Indicators of Compromise
| ID | Type | Indicator |
|---|---|---|
| CVE-2026-5946 | Vulnerability | CVE-2026-5946 |
| CVE-2026-5946 | Affected Product | BIND 9 |
Written by SCW Vulnerability Desk
Source & Attribution
| Source Platform | NVD |
| Channel | National Vulnerability Database |
| Published | May 20, 2026 at 16:16 UTC |
This content was AI-rewritten and enriched by Shimi's Cyber World based on the original source. All intellectual property rights remain with the original author.
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