Summary
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.
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.
Impact
In multi-tenant Kubernetes clusters, this flaw undermines DNS-based segmentation strategies.
Example scenario:
- ACL blocks access to *.admin.svc.cluster.local
- A rewrite rule maps public-name → admin.svc.cluster.local
- An unprivileged pod queries public-name
- ACL allows the request
- Rewrite exposes the internal admin service IP
This allows unauthorized service discovery and reconnaissance of restricted internal infrastructure.
CVE-2026-26017 has a CVSS score of 7.7 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.14.2); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
Has the problem been patched? What versions should users upgrade to?
Frequently Asked Questions
- What is CVE-2026-26017? CVE-2026-26017 is a high-severity security vulnerability in github.com/coredns/coredns (go), affecting versions < 1.14.2. It is fixed in 1.14.2.
- How severe is CVE-2026-26017? CVE-2026-26017 has a CVSS score of 7.7 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of github.com/coredns/coredns are affected by CVE-2026-26017? github.com/coredns/coredns (go) versions < 1.14.2 is affected.
- Is there a fix for CVE-2026-26017? Yes. CVE-2026-26017 is fixed in 1.14.2. Upgrade to this version or later.
- Is CVE-2026-26017 exploitable, and should I be worried? Whether CVE-2026-26017 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-26017 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-26017? Upgrade
github.com/coredns/corednsto 1.14.2 or later.