CVE-2026-33489
Description
A flaw was found in CoreDNS. An unauthorized remote client can exploit a vulnerability in the transfer plugin's Access Control List (ACL) stanza selection. This occurs when both a parent zone and a more-specific subzone are configured, and the longestMatch() function incorrectly uses a lexicographic string comparison. As a result, a permissive parent-zone transfer rule can override a restrictive subzone rule, allowing the client to perform zone transfers (AXFR/IXFR) for the subzone and retrieve its full zone contents. This leads to the disclosure of sensitive information.
Mitigation
To mitigate this vulnerability, ensure that the CoreDNS `transfer` plugin is configured with explicit and precise Access Control List (ACL) rules for all zones and subzones. Avoid broad parent-zone transfer rules that could inadvertently override more restrictive subzone configurations. If zone transfers are not required, disable the `transfer` plugin or restrict its access to only trusted internal networks using firewall rules or CoreDNS configuration directives. Always review and validate `transfer` plugin configurations to prevent unintended information disclosure.
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).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 6.5 | 7.5 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | Low | None | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | High | High | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | None | None | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Understanding the Weakness (CWE)
Other
Technical Impact: Varies by Context
This can lead to incorrect results and resultant weaknesses. For example, the code might inadvertently compare references to objects, instead of the relevant contents of those objects, causing two "equal" objects to be considered unequal.
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