HackSkills is an organized knowledge base of installable skills that gives AI agents practical security knowledge across areas such as web security, privilege escalation, reverse engineering, and digital forensics. It is intended for bug bounty work, penetration testing, CTF competitions, and authorized security research. The catalogue entries are the project's own master, category, and topic skills.
Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add yaklang/hack-skills --skill arbitrary-write-to-rcegit clone --depth 1 https://github.com/yaklang/hack-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/yaklang/hack-skills/arbitrary-write-to-rce)<a href="https://agentmods.dev/skills/yaklang/hack-skills/arbitrary-write-to-rce"><img src="https://agentmods.dev/badge/skills/yaklang/hack-skills/arbitrary-write-to-rce/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/yaklang/hack-skills/arbitrary-write-to-rce"><img src="https://agentmods.dev/badge/skills/yaklang/hack-skills/arbitrary-write-to-rce.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket warn
- Snyk fail
- NVIDIA SkillSpector warn
SkillSpector: 2 findings, up to high
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- high YARA Match · line 64 YARA rule matched a hack tool or exploit indicator (offensive tools, reconnaissance, privilege escalation, or exploit frameworks).Fix: Remove offensive tool references and exploit code. Legitimate agent skills should not contain penetration testing tools, exploit frameworks, or reconnaissance utilities.
- medium Excessive Agency · line 223 Skill grants unrestricted tool access without appropriate constraints. An agent with unfettered tool access can perform arbitrary actions including file modification, network requests, and code execution.Fix: Restrict tool access to only the tools required for the skill's stated purpose. Use an explicit allowlist rather than granting blanket access.
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00080 | $0.03783 |
| Opus 5 | $0.00040 | $0.01892 |
| Sonnet 5 | $0.00016 | $0.00757 |
| Haiku 4.5 | $0.00008 | $0.00378 |
Grade B, and why
arbitrary-write-to-rce scanned grade B with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 9d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Unrestricted tool accessmediumExcessive agency
A wildcard tool grant or "run any command" leaves no least-privilege boundary at all.
**Overwrite the kernel's `modprobe_path` to execute arbitrary commands as root.** Copies of this mod
4 near-identical copies found in the catalogue:
- arbitrary-write-to-rce — 100% identical, 4 lines differ
- arbitrary-write-to-rce — 100% identical, 0 lines differ
- arbitrary-write-to-rce — 100% identical, 0 lines differ
- arbitrary-write-to-rce — 100% identical, 0 lines differ
How it starts
The opening of the file, as written. The whole thing — 362 lines — stays where its author put it; the contents beside it link to each section on GitHub.
SKILL: Arbitrary Write to Code Execution — Expert Attack Playbook
AI LOAD INSTRUCTION: Expert techniques for converting an arbitrary write primitive into code execution. Covers every major overwrite target organized by glibc version compatibility: GOT, __malloc_hook, __free_hook, _IO_FILE vtable, __exit_funcs, TLS_dtor_list, _dl_fini, modprobe_path, .fini_array, C++ vtable, and setcontext gadget. This is the "last mile" skill. Base models often target hooks that no longer exist (post-glibc 2.34) or miss pointer mangling requirements.
0. RELATED ROUTING
- heap-exploitation — obtaining the arbitrary write via heap attacks
- format-string-exploitation — obtaining the arbitrary write via %n
- stack-overflow-and-rop — stack-based write primitives
- binary-protection-bypass — which targets are available given protection configuration
- heap-exploitation IO_FILE_EXPLOITATION.md — deep _IO_FILE structure exploitation
1. TARGET SELECTION BY GLIBC VERSION
| Target | glibc < 2.24 | 2.24–2.33 | ≥ 2.34 | Required Knowledge |
|---|---|---|---|---|
| GOT overwrite | OK (Partial RELRO) | OK (Partial RELRO) | OK (Partial RELRO) | Binary base |
__malloc_hook |
OK | OK | Removed | libc base |
__free_hook |
OK | OK | Removed | libc base |
__realloc_hook |
OK | OK | Removed | libc base |
_IO_FILE vtable (direct) |
OK | Vtable range check | Vtable range check | libc base + heap |
_IO_FILE via _IO_str_jumps |
N/A | OK (2.24–2.27) | Patched | libc base + heap |
_IO_FILE via _IO_wfile_jumps |
N/A | OK (≥ 2.28) | OK | libc base + heap |
__exit_funcs |
OK | OK | OK | libc base + pointer guard |
TLS_dtor_list |
N/A | N/A | OK | TLS addr + pointer guard |
_dl_fini / link_map |
OK | OK | OK | ld.so base |
modprobe_path (kernel) |
OK | OK | OK | Kernel base |
.fini_array |
OK | OK | OK | Binary base (if writable) |
| C++ vtable | OK | OK | OK | Object address + heap |
setcontext gadget |
OK | OK (changed in 2.29) | OK | libc base |
| Stack return address | Always | Always | Always | Stack address |
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 9d ago First seen · 362 lines · 80 tokens per session scan B e01c2f2b665d
arbitrary-write-to-rce is a skill published in the GitHub repository yaklang/hack-skills (2,133 stars, last pushed 2mo ago), licensed MIT. It adds 80 tokens to every session and 3,783 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it B with 1 finding (unrestricted tool access). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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