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container-k8s-escape

Security & auditing

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Updated 10-15 22:15

About this skill

Container Breakout & Kubernetes Escape

When to Activate

  • You have code execution inside a container/pod and want to break out to the host node
  • Auditing a Kubernetes cluster for RBAC privilege-escalation and lateral-movement paths
  • Assessing runc/containerd/BuildKit/Docker runtime versions against known escape CVEs
  • A pod is privileged, has dangerous capabilities, hostPath/hostPID/hostNetwork, or a mounted docker.sock
  • Attacking GPU/AI workloads using the NVIDIA Container Toolkit
  • Testing ingress-nginx / admission-controller exposure for unauthenticated RCE
  • Post-escape: pivoting from one node to full cluster takeover (kubelet, SA tokens, etcd, cloud IMDS)
  • Building Falco/Sigma detections for container-escape behavior (defensive validation)

Technique Map

Technique ATT&CK CWE Reference Script
runc working-dir fd leak escape (Leaky Vessels, CVE-2024-21626) T1611 CWE-403 references/runtime-cve-escapes.md scripts/runc_cwd_escape.py
runc masked-path / /dev/null symlink escape (CVE-2025-31133) T1611 CWE-367 references/runtime-cve-escapes.md scripts/runc_cwd_escape.py
runc /dev/console bind-mount + LSM bypass (CVE-2025-52565/52881) T1611 CWE-363 references/runtime-cve-escapes.md scripts/escape_enum.sh
BuildKit cache/teardown symlink escape (CVE-2024-23651/52/53) T1611 CWE-59 references/runtime-cve-escapes.md scripts/escape_enum.sh
Privileged / CAP_SYS_ADMIN cgroup release_agent escape T1611 CWE-269 references/privileged-misconfig-escape.md scripts/release_agent_escape.sh
core_pattern host-side code exec on crash T1611 CWE-269 references/privileged-misconfig-escape.md scripts/release_agent_escape.sh
hostPID + nsenter into PID 1 namespace T1611 CWE-668 references/privileged-misconfig-escape.md scripts/escape_enum.sh
Mounted docker.sock / containerd.sock host takeover T1610 CWE-668 references/privileged-misconfig-escape.md scripts/escape_enum.sh
hostPath / mount → write host filesystem T1611 CWE-22 references/privileged-misconfig-escape.md scripts/escape_enum.sh
NVIDIAScape LD_PRELOAD OCI-hook escape (CVE-2025-23266) T1611 CWE-426 references/nvidia-gpu-escape.md scripts/nvidiascape_build.sh
NVIDIA CT TOCTOU mount escape (CVE-2024-0132 / CVE-2025-23359) T1611 CWE-367 references/nvidia-gpu-escape.md scripts/nvidiascape_build.sh
K8s RBAC privesc (verb/wildcard/escalate, SA token theft) T1078.001 CWE-269 references/k8s-rbac-escalation.md scripts/k8s_rbac_audit.py
nodes/proxy GET → kubelet WebSocket exec RCE T1609 CWE-863 references/k8s-rbac-escalation.md scripts/kubelet_exec.py
Anonymous/authed kubelet API exec on :10250 T1609 CWE-306 references/k8s-rbac-escalation.md scripts/kubelet_exec.py
IngressNightmare unauth RCE (CVE-2025-1974 + annotation chain) T1190 CWE-94 references/ingress-admission-attacks.md scripts/escape_enum.sh
Node → cluster pivot (etcd, IMDS, SA-token harvest) T1613 CWE-552 references/node-host-pivot.md scripts/escape_enum.sh

Quick Start

# 0. Enumerate the container/pod context: caps, mounts, sockets, runtime versions, K8s creds
bash scripts/escape_enum.sh                 # run INSIDE the target container

# 1. Runtime-CVE path: detect vulnerable runc/BuildKit and run the cwd-fd escape (CVE-2024-21626)
python3 scripts/runc_cwd_escape.py --probe                       # try fd 7,8,9 -> host /
python3 scripts/runc_cwd_escape.py --cmd 'id; cat /etc/shadow'   # via docker -w or k8s revshell

# 2. Misconfig path: privileged / CAP_SYS_ADMIN -> cgroup release_agent host code exec
bash scripts/release_agent_escape.sh -c 'id > /tmp/escape_out'   # reads host PID list / runs cmd

# 3. GPU path: build a malicious image for NVIDIAScape (CVE-2025-23266)
bash scripts/nvidiascape_build.sh --cmd 'id; cat /etc/shadow' --tag evil-gpu:latest

# 4. K8s RBAC: audit who can escalate / reach the kubelet (needs a kubeconfig or in-pod SA token)
python3 scripts/k8s_rbac_audit.py --kubeconfig ~/.kube/config --dangerous

# 5. nodes/proxy or open kubelet -> exec into any pod on the node
python3 scripts/kubelet_exec.py --node 10.0.0.5 --pod kube-system/etcd-master \
        --container etcd --cmd 'cat /var/lib/etcd/...' --token "$SA_TOKEN"

Recommended tooling: deepce / cdk / amicontained (in-container recon), peirates (K8s pivot), kube-hunter (cluster scan), kubeletctl (kubelet API), crictl (post-escape node control), falco (defensive validation of every technique below).

OPSEC & Detection (summary)

Technique Telemetry / IOC Detection (Sigma/EDR/Falco) OPSEC note
runc cwd-fd escape (CVE-2024-21626) container process cwd under /proc/self/fd/N; getcwd ENOENT errors; host-path access from pid1 Falco Container Drift/unexpected host-fs read; alert on runtime < runc 1.1.12 No new files needed; works via -w/cwd only — very quiet, but lands on real host fs
runc 2025 trio (masked-path/console) symlink swap of /dev/null or /dev/pts/N; RW open of /proc/sysrq-trigger/core_pattern Falco "Write below /proc/sys"/sysrq; mount race anomalies Symlink swap is a timing race; on failure may crash host (sysrq) — loud
release_agent / core_pattern mount of cgroup/cgroup2; write to */release_agent or /proc/sys/kernel/core_pattern Falco Detect release_agent File Container Escapes; Sigma on write to core_pattern Requires CAP_SYS_ADMIN+mount; release_agent is cgroup-v1 only
nsenter / hostPID nsenter --target 1; process entering host mount/pid ns Falco "nsenter" / proc.name=nsenter in container; ATT&CK T1611 hostPID is visible in pod spec; nsenter is a strong IOC
docker.sock abuse /var/run/docker.sock mounted; curl --unix-socket create privileged container Falco "Docker socket access by unexpected proc"; new privileged container event Spawns a new privileged container — visible to docker/containerd events
NVIDIAScape (CVE-2025-23266) image ENV LD_PRELOAD=/proc/self/cwd/*.so; nvidia hook loads .so from container fs Falco shared-lib load by nvidia-ctk/hook from container path Needs only image push + run; no kernel bug — image scan catches the ENV
nodes/proxy → kubelet exec WebSocket GET to kubelet /exec//run on :10250; no API-server audit entry Runtime/L7 only — invisible to API audit & GuardDuty; monitor kubelet access log Bypasses API-server audit & admission entirely — extremely stealthy
K8s RBAC privesc / SA-token theft read of /var/run/secrets/.../token; can-i probes; bind to cluster-admin API audit create rolebindings/escalate; Falco Read SA token kubectl auth can-i probing is logged at API server
IngressNightmare (CVE-2025-1974) AdmissionReview with injected NGINX directive; .so loaded from /proc/<pid>/fd Sysdig/Falco "IngressNightmare"; shared-lib load from /proc in nginx Code runs during nginx -t validation; controller SA grabs all-namespace secrets

Deep Dives

  • references/runtime-cve-escapes.md — runc CVE-2024-21626 (working-dir fd leak), the Nov-2025 runc trio (CVE-2025-31133/52565/52881 masked-path & /dev/console), and the BuildKit Leaky Vessels CVEs, with full PoCs and version matrices.
  • references/privileged-misconfig-escape.md — --privileged/capability escapes: cgroup-v1 release_agent, core_pattern, hostPID+nsenter, mounted docker/containerd sockets, and hostPath// mounts, with complete scripts.
  • references/nvidia-gpu-escape.md — NVIDIAScape (CVE-2025-23266 LD_PRELOAD OCI-hook) and the CVE-2024-0132 / CVE-2025-23359 TOCTOU mount escapes in the NVIDIA Container Toolkit; build-and-run PoCs.
  • references/k8s-rbac-escalation.md — RBAC privilege escalation (wildcards, escalate/bind, pods/exec, impersonation), SA-token harvest, the nodes/proxy GET → kubelet WebSocket exec RCE, and open kubelet :10250.
  • references/ingress-admission-attacks.md — IngressNightmare (CVE-2025-1974 + the annotation-injection chain), admission-webhook abuse, and how a controller SA leads to cluster-wide secret theft.
  • references/node-host-pivot.md — post-escape playbook: from one node to the whole cluster — etcd looting, kubelet/crictl, SA-token mining across pods, cloud IMDS role theft, and the defensive counterweight.