GHSA-h8mm-c463-wjq3Published

CoreDNS transfer plugin subzone ACL bypass via lexicographic zone comparison

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cve-program · CVE-2026-33489

Published

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.

Source published: 5 May 2026 19:13:48 UTC
Source modified: 5 May 2026 19:43:06 UTC
Saved here: 23 Oct 2026 15:48:27 UTC
Source terms: CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

Source: cve-program · CVE Program Terms of Use. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

CVSS 4.0 · 8.2 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

euvd · EUVD-2026-27450

Published

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EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON.

Original publisher date fields

datePublished: May 5, 2026, 7:13:48 PM

dateUpdated: May 5, 2026, 7:43:06 PM

3 related source bulletins · separate from aliases

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

CVE-2026-33489

WID-SEC-W-2026-1283: CoreDNS: Mehrere Schwachstellen ermöglichen

CVE-2026-33190 · CVE-2026-33489 · CVE-2026-35579 · CVE-2026-32934 · CVE-2026-32936

openSUSE-SU-2026:20703-1: Security update for coredns

CVE-2026-27140 · CVE-2026-27143 · CVE-2026-27144 · CVE-2026-32282 · CVE-2026-32283 · CVE-2026-32288 · CVE-2026-32289 · CVE-2026-32934 · CVE-2026-32936 · CVE-2026-33190 · CVE-2026-33489 · CVE-2026-33810 · CVE-2026-35579

Source published: May 5, 2026, 7:13:48 PM (timezone not stated)
Source modified: May 5, 2026, 7:43:06 PM (timezone not stated)
Saved here: 15 Nov 2026 10:03:29 UTC
Source terms: ENISA EUVD · source terms and attribution apply

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Source: euvd · ENISA EUVD · source terms and attribution apply. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

EUVD CVSS 4.0 · 8.2 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

nvd · CVE-2026-33489

Published

Additional publisher context

NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON.

Source analysis status: Analyzed

Weakness classifications: CWE-863

Original publisher date fields

published: 2026-05-05T20:16:36.627

lastModified: 2026-07-24T23:10:00.563

1 source CPE criteria · context only

cpe:2.3:a:coredns.io:coredns:*:*:*:*:*:*:*:*

The original JSON retains the logical configuration operators, exclusions and version bounds.

Source published: 5 May 2026 20:16:36 UTC
Source modified: 24 Jul 2026 23:10:00 UTC
Saved here: 25 Oct 2026 08:17:24 UTC
Source terms: NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

Source: nvd · NIST NVD usage terms; underlying source attribution retained. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

CVSS 4.0 · [email protected] · Secondary · 8.2 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS 3.1 · [email protected] · Primary · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

osv · GHSA-h8mm-c463-wjq3

Published

### Summary CoreDNS' transfer plugin can select the wrong ACL stanza when both a parent zone and a more-specific subzone are configured. A permissive parent-zone transfer rule can override a restrictive subzone rule (name-dependent), allowing an unauthorized client to perform AXFR/IXFR for the subzone and retrieve its zone contents. ### Details In plugin/transfer/transfer.go, stanza selection is implemented by longestMatch(), which is documented as "longest zone match wins", but it actually chooses the winner via a lexicographic string comparison: - zone := "" // longest zone match wins (plugin/transfer/transfer.go) - if z > zone { zone = z; x = xfr } (plugin/transfer/transfer.go) So, a parent zone like example.org. can beat a child zone like a.example.org. purely due to lexicographic ordering ("example.org." > "a.example.org."), even though the child zone is the longer/more specific suffix match. The bypass is data-dependent (some child labels will win, some will lose), making it operationally non-intuitive. ### PoC 1. Adjust COREDNS_BIN in the PoC to point at right path (see the top-level const definitions for tunables as well) 2. Run python3 ./acl-repro.py 3. Expected output: *** Baseline (only subzone transfer rule) *** axfr a.example.org.: rcode=5 ancount=0 (expected REFUSED=5) *** Candidate (add permissive parent transfer rule) *** axfr a.example.org.: rcode=0 ancount=5 (expected NOERROR=0 with ancount>0) *** OK *** Subzone transfer ACL bypass reproduced: adding a permissive parent-zone stanza can override a stricter child-zone stanza due to lexicographic zone selection. ### Impact Unauthorized zone transfer can expose full zone contents to a remote network client that was intended to be denied by a subzone-specific transfer policy.

Source published: 28 Apr 2026 22:44:39 UTC
Source modified: 10 Sep 2026 03:50:44 UTC
Saved here: 24 Oct 2026 13:19:41 UTC
Source terms: GitHub Advisory Database · CC-BY-4.0

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Source: osv · GitHub Advisory Database · CC-BY-4.0. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Publisher rating · HIGH

osv · GO-2026-5417

Published

CoreDNS' transfer stanza selection uses lexicographic compare (subzone ACL bypass) in github.com/coredns/coredns

Source published: 25 Jun 2026 22:34:31 UTC
Source modified: 25 Jun 2026 23:00:16 UTC
Saved here: 24 Oct 2026 13:19:41 UTC
Source terms: OSV · upstream source license applies

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Source: osv · OSV · upstream source license applies. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.