CVE-2026-33489: coredns Auth Bypass — Exploit & Fix

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.

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CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS — Exploit Prediction

0.0002

Probability of exploitation

0.03%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-863 Incorrect Authorization

Affected Products

Vendor	Product	Versions
coredns.io	coredns	< 1.14.3

References

Advisories & Patches

https://github.com/coredns/coredns/security/advisories/GHSA-h8mm-c463-wjq3 https://github.com/coredns/coredns/security/advisories/GHSA-h8mm-c463-wjq3

Exploits

https://github.com/coredns/coredns/security/advisories/GHSA-h8mm-c463-wjq3 https://github.com/coredns/coredns/security/advisories/GHSA-h8mm-c463-wjq3

Other References

https://github.com/coredns/coredns/releases/tag/v1.14.3

Frequently Asked Questions

What is CVE-2026-33489? +

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. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-33489? +

CVE-2026-33489 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0002, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-33489? +

CVE-2026-33489 affects products from coredns.io, specifically: coredns. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-33489? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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