offensive-toctou skillA
offensive-toctou is agent-read markdown (skill) from snailsploit/claude-red: Time-of-Check / Time-of-Use (TOCTOU) race condition exploitation methodology across binary, kernel, filesystem, web, and container layers. Covers symbolic-link races (open/access/stat split), file-descriptor races, fopen/realpath traversal races, /proc and procfs races, FUSE-backed slow-fs races to widen the window, ptrace and signal races, kernel double-fetch / userspace pointer races, container/runc/symlink escape primitives, kubernetes admission/authz TOCTOU, web auth-vs-authz TOCTOU, JWT-cla.
Indexed from public GitHub and served as immutable, content-addressed versions. Install it pinned to an exact SHA-256 with the mdr CLI, and every file is verified against the hash recorded here before it reaches your agent. The deterministic audit below grades the latest version, and the same file always earns the same grade.
What the file says
# TOCTOU — Time-of-Check / Time-of-Use Exploitation
A TOCTOU bug exists wherever code checks a property (file owner, path target, token validity, balance) and then acts on it as if the property still holds. Between check and use is a window — your job is to widen it and swap the underlying object.
## Quick Workflow
1. Identify the **check** (syscall, function, validation step) and the **use** (the privileged action)
2. Confirm the check and use don't operate on the same kernel object (FD, inode, atomic snapshot)
3. Build a primitive that swaps the object between check and use (symlink, mount, mv, parallel request)
4. **Widen the window** with FUSE, slow filesystems, scheduler tricks, or single-packet HTTP/2
5. Run a tight loop and confirm the post-use state corresponds to the swapped target
---
## The Core Pattern
```c
// Vulnerable
if (access(path, W_OK) == 0) { // check — resolves "path" now
fd = open(path, O_WRONLY); // use — re-resolves "path" later
write(fd, attacker_data, n);
}
```
Between `access` and `open`, an attacker replaces `path` with a symlink to `/etc/shadow`. The check sees an attacker-owned file; the use opens shadow as root.
…Read the whole file at its exact version.
How to install
mdr add snailsploit/claude-red/offensive-toctou@git:20260506.70e0c89mdr add snailsploit/claude-red/offensive-toctou@sha256:8c7fb9790b1853ecPin to a label to follow the author's releases, or to a sha256 to freeze the exact bytes forever. Either way the resolved hash is written to mdr.lock, and mdr install reproduces it on any machine.
[](https://markdownregistry.com/a/art_sjkpgo34yxz2nn6k)
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Versions
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (12855 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
snailsploit/claude-red · 6,831 stars · license MIT · pushed 2026-09-19 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_sjkpgo34yxz2nn6k GET https://markdownregistry.com/api/v1/resolve?ref=snailsploit/claude-red/offensive-toctou GET https://markdownregistry.com/api/v1/blob/8c7fb9790b1853ecf5dfa23fe85b8fa0d1967c20a7ffe04752a6ac4c2253636f
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