CVE-2026-26017

CoreDNS ACL Bypass

CVSS 3.1 7.7 HIGHEUVD CVSS 3.1 7.7 CVSS 3.1 · [email protected] · Secondary 7.7 HIGHCVSS 3.1 · [email protected] · Primary 6.3 MEDIUMCVSS 3.1 · 0b0ca135-0b70-47e7-9f44-1890c2a1c46c · Secondary 7.7 HIGHCVSS_V3 Publisher rating HIGHFixed by github.com/coredns/coredns 1.14.2osv · severity unknownFixed by github.com/coredns/coredns 1.14.2KEV status unknown

Original advisory

cve-program · CVE-2026-26017

Published

CoreDNS is a DNS server that chains plugins. Prior to version 1.14.2, a logical vulnerability in CoreDNS allows DNS access controls to be bypassed due to the default execution order of plugins. Security plugins such as acl are evaluated before the rewrite plugin, resulting in a Time-of-Check Time-of-Use (TOCTOU) flaw. This issue has been patched in version 1.14.2.

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euvd · EUVD-2026-10042

Published

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nvd · CVE-2026-26017

Published

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osv · GHSA-c9v3-4pv7-87pr

Published

A logical vulnerability in CoreDNS allows DNS access controls to be bypassed due to the default execution order of plugins. Security plugins such as acl are evaluated before the rewrite plugin, resulting in a Time-of-Check Time-of-Use (TOCTOU) flaw. ### Impact In multi-tenant Kubernetes clusters, this flaw undermines DNS-based segmentation strategies. Example scenario: 1. ACL blocks access to *.admin.svc.cluster.local 2. A rewrite rule maps public-name → admin.svc.cluster.local 3. An unprivileged pod queries public-name 4. ACL allows the request 5. Rewrite exposes the internal admin service IP This allows unauthorized service discovery and reconnaissance of restricted internal infrastructure. ### Patches _Has the problem been patched? What versions should users upgrade to?_ ### Workarounds - Reorder the default plugin.cfg so that: - rewrite and other normalization plugins run before acl, opa, and firewall - Ensure all access control checks are applied after name normalization.

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osv · GO-2026-4630

Published

CoreDNS ACL Bypass in github.com/coredns/coredns

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Affected versions, risk and source history

Exploitation and risk

Source status

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Risk history

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Advisory history

14 saved versions

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15 Nov 2026 12:06:13 UTC