Detect Toctou Races
Detection and hardening methodology for TOCTOU (time-of-check to time-of-use) file race conditions used for local privilege escalation, where an attacker swaps a symlink, hardlink, junction, or file between a privileged process's check and its use (MITRE ATT&CK T1068, setuid case T1548.001). ATT&CK has no TOCTOU-specific technique, so detection keys off observable edges: Linux auditd SYSCALL/PATH records for symlink/link/rename, the fs.protected_* sysctls, Falco, Sysmon for Linux, osquery; Windows Sysmon FileCreate (Event ID 11) and Security object-access auditing (4663/4656). Gives the defender view of the attack, a hunt, public rule sources, and a hardening plan. Use when investigating a suspected symlink or race-condition local root, triaging a privileged process writing through a world-writable path, hunting for symlink-swap attempts in /tmp, auditing services operating on user-controllable paths, or writing TOCTOU detections.
Security AStatic scan found no risk patternsHow grading works ›
What this skill does
Detect Toctou Races is a community-contributed Claude Code skill in the web-security sub-category. It ships as a SKILL.md file that Claude Code auto-discovers under ~/.claude/skills/detect-toctou-races/ and loads when your prompt matches the skill's trigger.
When to invoke it: Use when investigating a suspected symlink or race-condition local root, triaging a privileged process writing through a world-writable path, hunting for symlink-swap attempts in /tmp, auditing services operating on user-controllable paths, or writing TOCTOU detections.
Who uses this skill
The Detect Toctou Races Claude Code skill is built for security engineers, penetration testers, DevSecOps practitioners, and development teams hardening codebases and infrastructure. It's part of ClaudSkills (also referred to as Claude Skills or Claude Code Skills) — the open community-curated registry of 211,000+ SKILL.md files for Anthropic's Claude Code agent and the wider Claude ecosystem (Claude API, Claude Agent SDK).
How to install
Free
Manual install (2 steps)
mkdir -p ~/.claude/skills/detect-toctou-races
curl -L https://claudskills.com/skills/detect-toctou-races/SKILL.md \
-o ~/.claude/skills/detect-toctou-races/SKILL.md
Or just download SKILL.md directly and drop it into ~/.claude/skills/detect-toctou-races/. Claude Code auto-discovers it on next session.
Skills live at ~/.claude/skills/detect-toctou-races/SKILL.md on macOS/Linux, or %USERPROFILE%\.claude\skills\detect-toctou-races\SKILL.md on Windows. See the full install guide for step-by-step instructions.
Telegram
📱 Install from your phone or desktop Telegram
Open @claudskills_bot on Telegram, tap Open Desktop App, and the desktop app installs this skill for you. Or share the bot link with a colleague — they get the same one-tap install. Learn more →
Pro
One-click install via the desktop app
The ClaudSkills desktop app installs any skill directly into ~/.claude/skills/ with one click — no terminal required. Pro starts at $9/mo or $149 lifetime.
Pro
For the full experience including quality scoring and one-click install features for each skill — upgrade to Pro.
Frequently asked questions
How do I install the Detect Toctou Races Claude Code skill?
Install via the ClaudSkills desktop app (one click) or copy
SKILL.md from the source repository to
~/.claude/skills/detect-toctou-races/SKILL.md and restart Claude Code. Both flows are detailed at
claudskills.com/install/.
What does the Detect Toctou Races skill do?
Detection and hardening methodology for TOCTOU (time-of-check to time-of-use) file race conditions used for local privilege escalation, where an attacker swaps a symlink, hardlink, junction, or file between a privileged process's check and its use (MITRE ATT&CK T1068, setuid case T1548.001). ATT&CK has no TOCTOU-specific technique, so detection keys off observable edges: Linux auditd SYSCALL/PATH records for symlink/link/rename, the fs.protected_* sysctls, Falco, Sysmon for Linux, osquery; Windows Sysmon FileCreate (Event ID 11) and Security object-access auditing (4663/4656). Gives the defender view of the attack, a hunt, public rule sources, and a hardening plan. Use when investigating a suspected symlink or race-condition local root, triaging a privileged process writing through a world-writable path, hunting for symlink-swap attempts in /tmp, auditing services operating on user-controllable paths, or writing TOCTOU detections.
Is this skill free to install?
Yes. ClaudSkills is an open registry — every skill keeps its source repository's license, and manual install via copy is free. ClaudSkills Pro ($9/mo, $79/yr, or $149 one-time) adds one-click install via the desktop app and a multi-signal Quality Score.
When should I use the Detect Toctou Races skill?
Use Detect Toctou Races when your Claude Code task falls under the Security category — specifically in the web security area. Claude Code auto-discovers installed skills and invokes the right one based on the task description, so you can also ask Claude directly (e.g. "use Detect Toctou Races" or describe the task and let Claude pick). Browse related skills at
/category/security/.
What is a Claude Code skill and how does the Detect Toctou Races skill fit in?
A Claude Code skill is a
SKILL.md file that lives under
~/.claude/skills/<name>/ and tells the Claude Code CLI agent how to perform a specific task (instructions, prompts, allowed tools). Skills are auto-discovered at session start. Detect Toctou Races is one of 67,000+ skills indexed in the open ClaudSkills catalog, classified under the Security category. Learn more at
/learn/what-is-a-claude-skill/.
Attribution & license
Cite this skill
If you reference this skill in a blog post, paper, or documentation, you can cite it as:
APA
umbrasec-labs. (2026). Detect Toctou Races [Claude Code skill]. ClaudSkills. https://claudskills.com/skills/detect-toctou-races/
BibTeX
@misc{detect-toctou-races-2026,
author = {umbrasec-labs},
title = {Detect Toctou Races [Claude Code skill]},
year = {2026},
publisher = {ClaudSkills},
url = {https://claudskills.com/skills/detect-toctou-races/}
}Embed this skill
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Security scan
Grade A · scanned 2026-10-25 — free static scan against the OWASP Agentic Skills Top 10.
The scan flagged 1 of 10 categories (filesystem), including lower-severity patterns. Patterns shown inside code fences are weighted as examples rather than instructions — read the grading methodology for what this does and does not guarantee.
- ✓ Prompt injection
- ✓ Data exfiltration
- ✓ Supply chain
- ✓ Reverse shell
- ✓ Credentials
- ✓ Execution
- ⚠ Filesystem
- ✓ Persistence
- ✓ Obfuscation
- ✓ Network
Show this grade on your repo (click to copy):
[](https://claudskills.com/skills/detect-toctou-races/#security)
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