Detect Linux Kernel cgroup v1 release_agent Privilege Escalation (CVE-2022-0492) in Splunk
CVE-2022-0492 is a Linux kernel vulnerability (CWE-287/CWE-862) in the cgroup v1 release_agent mechanism. A local unprivileged user can exploit improper capability checks to write to /sys/fs/cgroup/*/release_agent and execute arbitrary commands as root, enabling container escape and full host compromise. This vulnerability is listed on CISA KEV, indicating active exploitation in the wild.
MITRE ATT&CK
SPL Detection Query
index=linux_security sourcetype IN ("sysmon_linux", "auditd", "osquery")
(
(EventCode=11 OR event_type="WRITE" OR event_type="OPEN")
TargetFilename IN ("/sys/fs/cgroup/*/release_agent", "/sys/fs/cgroup/memory/release_agent", "/sys/fs/cgroup/cpu/release_agent")
)
OR
(
(EventCode=1 OR event_type="execve")
(
(process IN ("sh","bash","dash") CommandLine="*release_agent*")
OR (process IN ("unshare","nsenter") CommandLine="*/sys/fs/cgroup*")
OR CommandLine="*notify_on_release*"
)
)
| eval risk_score=case(
match(TargetFilename,"release_agent"), 95,
match(CommandLine,"unshare.*cgroup"), 85,
true(), 70
)
| eval cve="CVE-2022-0492"
| table _time, host, user, process, CommandLine, TargetFilename, risk_score, cve
| sort -risk_scoreSPL query detecting file writes to cgroup release_agent paths, shell executions referencing release_agent, and namespace manipulation (unshare/nsenter) combined with cgroup access indicative of CVE-2022-0492.
Data Sources
Required Sourcetypes
False Positives & Tuning
- Container orchestration systems (Kubernetes kubelet, Docker daemon) performing legitimate cgroup lifecycle management
- System tuning scripts that configure cgroup release behavior
- Security testing or red team exercises against non-production systems
- Kernel developers testing cgroup functionality in controlled environments
Other platforms for CVE-2022-0492
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 1Write payload to cgroup release_agent (non-privileged namespace simulation)
Expected signal: Process event for unshare with -UrmC flags; file write event to path matching /sys/fs/cgroup/*/release_agent or the tmp mount path; child bash process inheriting modified cgroup namespace
- Test 2Enumerate cgroup v1 hierarchy for exploitable release_agent
Expected signal: Process event for sh/bash with find commands targeting /sys/fs/cgroup paths; multiple file read events against notify_on_release and release_agent pseudo-files
- Test 3Container escape simulation via cgroup release_agent (lab environment)
Expected signal: Docker daemon log showing privileged container creation; host-level process events for cgroup mount, release_agent write; if successful: unexpected process spawned outside container namespace with UID 0; file creation event for escape_proof.txt on host
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