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.
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.
Has the problem been patched? What versions should users upgrade to?
| Score | Percentile |
|---|---|
| 0.06% | 18.45% |
| Base score | Version | Severity | Vector |
|---|---|---|---|
| 7.7 | 3.1 | — |
|
| Type | Value |
|---|---|
| GHSA | GHSA-c9v3-4pv7-87pr ↗ |
| CVE | CVE-2026-26017 ↗ |
| CWE id | Name |
|---|---|
| CWE-367 | Time-of-check Time-of-use (TOCTOU) Race Condition |
Vulnerable version ranges and first patched releases as published by GitHub.
| Ecosystem | Package | Vulnerable range | First patched | Vulnerable functions |
|---|---|---|---|---|
| go | github.com/coredns/coredns | < 1.14.2 | 1.14.2 | — |