CVE-2026-19666
Description
A flaw was found in BIND. When a resolver is configured to use DNS64, a specially crafted, malformed answer from an authoritative server can cause the named process to exit unexpectedly. This can lead to a Denial of Service (DoS) for clients relying on the affected resolver.
Statement
Important: This denial of service vulnerability affects BIND resolvers configured to use the dns64 feature. A specially crafted malformed DNS64 response from an authoritative server can cause the named process to unexpectedly terminate, leading to service unavailability. Exploitation requires the dns64 feature to be explicitly enabled in the resolver's configuration.
Mitigation
To mitigate this issue, disable the `dns64` feature in the BIND resolver configuration if it is not required. This can be done by removing or commenting out the `dns64` configuration block in `named.conf` or related configuration files. After modifying the configuration, the BIND service (`named`) must be reloaded or restarted for the changes to take effect. This action may temporarily interrupt DNS resolution services.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart
An attacker that can trigger an assert statement can still lead to a denial of service if the relevant code can be triggered by an attacker, and if the scope of the assert() extends beyond the attacker's own session.
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