Detect Fission Container Executor PodSpec Injection - Node Escape Attempt in CrowdStrike LogScale
Detects exploitation of CVE-2026-50563, a critical privilege escalation vulnerability in Fission serverless framework (<=1.23.0). The container executor allows unauthenticated or low-privileged users to inject arbitrary PodSpec fields into function pods, enabling container escape to the underlying Kubernetes node. Attackers can inject hostPID, hostNetwork, privileged containers, hostPath volume mounts, or custom service accounts to achieve full node compromise.
MITRE ATT&CK
LogScale Detection Query
#event_simpleName IN ("ProcessRollup2", "NetworkConnectIP4", "SyntheticProcessRollup2")
| NamespaceName = /^fission/i
| (
FileName IN ["nsenter", "unshare", "chroot"]
OR CommandLine = /\/proc\/1\/root|\/host\/|\/hostfs\//
OR CommandLine = /--target 1|--mount.*proc|--pid.*host/
)
| ParentBaseFileName IN ["fission-fetcher", "env", "sh", "bash", "python3", "node"]
| groupby([aid, ComputerName, NamespaceName, FileName, CommandLine, UserName, ParentBaseFileName])
| rename aid as AgentID
| eval CVE = "CVE-2026-50563"
| eval Severity = "Critical"
| eval ThreatDescription = "Fission container executor PodSpec injection - potential node escape"
| sort -@timestampCrowdStrike Falcon Query Language detection for process execution patterns consistent with container escape following Fission PodSpec injection exploitation.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate use of nsenter by CrowdStrike Falcon sensor itself for container inspection capabilities
- Kubernetes CSI driver operations that use chroot during volume mount operations on Fission function nodes
- Authorized incident responders using nsenter during active investigation of Fission function pods
Other platforms for CVE-2026-50563
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 1Fission PodSpec Injection - hostPID Escape
Expected signal: Kubernetes audit log entry with verb=create, objectRef.resource=pods, objectRef.namespace=fission-function, requestObject.spec.hostPID=true. Container process list will show host-level PIDs including kubelet, containerd, and other node processes.
- Test 2Fission PodSpec Injection - Privileged Container with hostPath Root Mount
Expected signal: Kubernetes audit log with requestObject.spec.containers[0].securityContext.privileged=true and requestObject.spec.volumes containing hostPath.path=/. Container runtime logs showing privileged container start. Node-level filesystem access to /etc/passwd and hostname file.
- Test 3Fission Container Escape via nsenter After PodSpec Injection
Expected signal: Process telemetry on Kubernetes node showing nsenter executed with --target 1 argument. Host PID 1 (init/systemd) namespace join event visible in node audit logs. Container log output matching host OS details rather than Alpine container OS.
References (6)
- https://github.com/fission/fission/security/advisories/GHSA-v455-mv2v-5g92
- https://nvd.nist.gov/vuln/detail/CVE-2026-50563
- https://github.com/fission/fission/pull/3391
- https://github.com/fission/fission/commit/e484df8460bb4e8026e24210120602aa7f181f64
- https://github.com/fission/fission/releases/tag/v1.24.0
- https://github.com/advisories/GHSA-v455-mv2v-5g92
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