High priorityDisclosed

Advisory · CVE-2026-122306

Pathological wildcard patterns can exhaust Kyverno's admission controller

Kyverno before 1.19.2 lets namespaced policy authors exhaust admission controller CPU with pathological wildcard patterns evaluated by ValidateMatchExcludeConflict, pinning cores and causing cluster-wide webhook timeouts. Kyverno rates it CVSS 4.0 8.3.

Advisory published November 5, 2026Independent summary
Vendor
Kyverno
Product
Kyverno
Identifier / CWE
CVE-2026-122306
CWE-407
Action timing
Immediate
ELI5

Explain it like I’m five

A carefully shaped wildcard pattern makes the matching code do exponentially more work than it should, until the admission controller is too busy to answer anyone.

SIMPLIFIED_ATTACK_PATH04 STEPS
  1. 01Policy with crafted patterns

    A namespaced policy author submits a Policy with crafted match and exclude names.

  2. 02Expensive matching

    ValidateMatchExcludeConflict evaluates the pathological wildcard patterns.

  3. 03CPU pinned

    Cores are pinned by the matching work and the admission controller stalls.

  4. 04Webhook timeouts

    Cluster-wide webhook timeouts block resource operations.

What happened

Kyverno disclosed CVE-2026-122306 for Kyverno before 1.19.2. Namespaced policy authors can exhaust admission controller CPU by submitting pathological wildcard patterns: a Policy with crafted match and exclude names evaluated by ValidateMatchExcludeConflict pins cores and causes cluster-wide webhook timeouts that block resource operations.

The advisory rates it CVSS 4.0 8.3 and identifies Kyverno 1.19.2 as the fixed release.

What to do

  1. Inventory Kyverno installations and confirm the deployed version.
  2. Upgrade affected installations to Kyverno 1.19.2 or later using the project release guidance.
  3. While remediation is underway, review new Policies for unusual match and exclude patterns.
  4. Watch admission webhook latency and CPU for signs of wildcard matching abuse.
  5. Audit recently created Policies for crafted patterns.

Management note

This is a low-privilege denial of service against shared control-plane infrastructure. It takes one tenant with policy-writing rights to freeze admissions for everyone, so do not leave it for a later cycle.