CVE-2026-33489: CoreDNS transfer plugin subzone ACL bypass via lexicographic zone comparison

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-05-05 · updated 2026-07-24
Weakness: CWE-863

Description

CoreDNS is a DNS server that chains plugins. In versions prior to 1.14.3, the transfer plugin can select the wrong ACL stanza when both a parent zone and a more-specific subzone are configured. The longestMatch() function in plugin/transfer/transfer.go uses a lexicographic string comparison instead of an actual longest-suffix match to select the winning zone. As a result, a permissive parent-zone transfer rule can override a restrictive subzone rule depending on zone name ordering (e.g., "example.org." > "a.example.org." lexicographically). This allows an unauthorized remote client to perform AXFR/IXFR for the subzone and retrieve its full zone contents. This issue has been fixed in version 1.14.3.

Affected products

coredns: before 1.14.3 — fixed in 1.14.3

How to fix

Upgrade to a fixed version: coredns 1.14.3. Check the vendor advisory for mitigations.

References

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