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GHSA-c9v3-4pv7-87pr

HighCVSS 7.7 / 10
Published Mar 6, 2026·Last modified May 5, 2026
Affected Components(0)

No affected components available

Description

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.
Risk Scores
Base Score
7.7

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The vulnerability can affect other systems as well, not just the initial system. There is a high impact on the confidentiality of the information.

Threat Intelligence
7.1

Exploitation activity has been observed. Apply available patches or mitigations urgently.

EPSS
0.39%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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High severity
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