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Unlock with Pro - from £29/user/moDetect Kube-logging Logging Operator Fluentd Configuration Injection RCE (CVE-2026-54680) in Elastic Security
Detects exploitation of CVE-2026-54680, a critical (CVSS 9.9) configuration injection vulnerability in kube-logging logging-operator (versions prior to the 0.0.0-20260608145523-cf437d7f1e05 pseudo-version / 6.6.0 release) that allows an attacker with the ability to influence Fluentd/Fluent Bit configuration inputs (e.g. via Flow/ClusterFlow/Output CRDs, log forwarding pipelines, or unsanitized log fields reflected into config templates) to inject arbitrary Fluentd configuration directives. This injection can lead to remote code execution via Fluentd's exec plugin, ruby code blocks, or file-based output writes, potentially compromising the logging-operator pod and any Kubernetes service account/token it holds, enabling lateral movement and cluster compromise.
MITRE ATT&CK
Elastic Detection Query
sequence by k8s.namespace with maxspan=10m
[any where event.dataset == "kubernetes.audit_logs" and
kubernetes.audit.objectRef.resource in ("flows", "clusterflows", "outputs", "clusteroutputs", "loggings") and
kubernetes.audit.verb in ("create", "update", "patch") and
kubernetes.audit.requestObject.raw : ("*exec*", "*ruby*", "*system(*", "*/bin/sh*", "*/bin/bash*")]
[any where event.dataset in ("kubernetes.container_logs") and
(process.name in ("fluentd", "fluent-bit") or container.name : "*logging-operator*") and
(message : "*invalid configuration*" or message : "*parse error*" or message : "*exec_filter*")]Correlates a Kubernetes audit event where a Flow/ClusterFlow/Output/Logging resource is created or modified with an embedded exec/ruby/shell directive, followed within 10 minutes by anomalous fluentd/fluent-bit container log activity, indicating likely CVE-2026-54680 exploitation.
Data Sources
Required Tables
False Positives & Tuning
- Approved configuration changes deploying legitimate exec output plugins
- Routine configuration reload errors unrelated to injection
- Scheduled maintenance windows where Flow resources are frequently patched by CI/CD
Other platforms for CVE-2026-54680
Testing Methodology
Validate this detection against 3 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 1Inject exec directive via ClusterFlow CRD
Expected signal: Kubernetes audit log entries for create operations on ClusterFlow and ClusterOutput resources containing an 'exec' block, followed by fluentd operator reconciliation logs regenerating the rendered configuration.
- Test 2Inject ruby eval block into Output configuration
Expected signal: Audit log capturing the Output resource creation with enableRuby=true and a system() call embedded in the record template; fluentd pod logs showing plugin reconfiguration.
- Test 3Simulate command execution artifact from compromised fluentd pod
Expected signal: Container runtime/EDR process execution events for /bin/sh, id, whoami, and cat commands executed inside the fluentd pod, plus Kubernetes audit log entry for the 'pods/exec' subresource.
References (4)
- https://github.com/kube-logging/logging-operator/security/advisories/GHSA-mjqf-28ph-426h
- https://github.com/kube-logging/logging-operator/commit/cf437d7f1e056c78740bf5716ac8bdebcf002425
- https://github.com/kube-logging/logging-operator/releases/tag/6.6.0
- https://github.com/advisories/GHSA-mjqf-28ph-426h
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