Detect Rancher Fleet Cross-Namespace Secret Disclosure via Unvalidated valuesFrom References in CrowdStrike LogScale
CVE-2026-44935 is a critical (CVSS 9.9) authorization bypass vulnerability in Rancher Fleet's Helm Deployer affecting versions 0.12.0-0.12.14, 0.13.0-0.13.10, 0.14.0-0.14.5, and 0.15.0-0.15.1. The Helm Deployer fails to validate namespace boundaries when resolving `valuesFrom` references in GitRepo or Bundle resources, allowing an attacker with access to one namespace to craft a GitRepo or Bundle that references Secrets or ConfigMaps from arbitrary namespaces including cluster-scoped secrets. This constitutes an incorrect authorization check (CWE-863) that can expose credentials, API keys, and sensitive configuration from namespaces the attacker should not have access to. A public PoC is available.
MITRE ATT&CK
- Tactic
- Credential Access Discovery
LogScale Detection Query
#event_simpleName=KubernetesAuditEvent
| verb IN ("get", "list", "watch")
| objectRefResource IN ("secrets", "configmaps")
| userUsername = /system:serviceaccount:.*fleet.*/i
| responseStatusCode = 200
| eval source_namespace=replace(userUsername, /system:serviceaccount:([^:]+):.*/, "\\1")
| where objectRefNamespace != source_namespace AND isNotNull(objectRefNamespace)
| stats count() AS cross_ns_count, values(objectRefName) AS secret_names, values(objectRefNamespace) AS target_namespaces BY userUsername, source_namespace, ClusterName
| where cross_ns_count > 0
| sort -cross_ns_countCrowdStrike Falcon LogScale (CQL) query identifying Rancher Fleet service account cross-namespace secret reads consistent with CVE-2026-44935 exploitation via unvalidated valuesFrom references.
Data Sources
Required Tables
False Positives & Tuning
- Fleet workloads with CrowdStrike exclusions or namespace-level monitoring gaps
- Kubernetes clusters where audit logging verbosity does not capture secret GET operations
- Service accounts with 'fleet' in their name that are not part of Rancher Fleet
Other platforms for CVE-2026-44935
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Simulate Fleet valuesFrom Cross-Namespace Secret Read
Expected signal: Kubernetes audit log entry: verb=get, resource=secrets, objectRef.name=victim-secret, objectRef.namespace=fleet-test-victim, user.username=system:serviceaccount:fleet-test-attacker:fleet-*, responseStatus.code=200
- Test 2Enumerate Existing GitRepo valuesFrom Cross-Namespace References
Expected signal: Script output listing cross-namespace references; Kubernetes API audit logs for GET gitrepos and GET bundles at cluster scope
- Test 3Fleet Service Account RBAC Permission Audit for Secret Access
Expected signal: kubectl auth can-i commands generate Kubernetes audit log entries for SubjectAccessReview API calls; RBAC audit output identifies over-privileged Fleet service accounts
- Test 4Monitor Fleet Controller Live for Cross-Namespace Secret Access Events
Expected signal: Real-time stdout alerts for each cross-namespace secret or configmap read event matching Fleet service account patterns
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