druid-javascript-rce SKILL.md skillA
druid-javascript-rce from cxcscmu/skilllearnbench is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add cxcscmu/skilllearnbench/druid-javascript-rce@git:20260424.d50cf5aPins git:20260424.d50cf5a in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- cxcscmu/skilllearnbench
- Path
skills/b1-one-shot-claude-opus-4-6/fix-security-bug/druid-javascript-rce/SKILL.md- Versions recorded
- 1
- Latest version
- git:20260424.d50cf5a, committed Apr 24, 2026
- Size
- 1,956 bytes
- Repository stars
- 91
- License
- MIT
Apache Druid JavaScript RCE vulnerability (CVE-2021-25646) fix via @JacksonInject hardening and constructor validation.
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
# Apache Druid JavaScript RCE Vulnerability
## Overview
Apache Druid 0.20.0 allows authenticated users to execute arbitrary server-side code through JavaScript-based features (filters, aggregators, extraction functions, etc.) even when JavaScript is disabled via `druid.javascript.enabled=false`.
## Root Cause
All JavaScript-related classes use `@JacksonInject JavaScriptConfig config` to receive the server-side JavaScript configuration. Jackson's default behavior allows JSON input to override injected values via an empty key `""`.
## Affected Classes
1. `JavaScriptDimFilter` - processing module
2. `JavaScriptAggregatorFactory` - processing module
3. `JavaScriptExtractionFn` - processing module
4. `JavaScriptPostAggregator` - processing module
5. `JavaScriptParseSpec` - core module
6. `JavaScriptTieredBrokerSelectorStrategy` - server module (already has constructor check)
## Fix Strategy
For each affected class:
1. Change `@JacksonInject` to `@JacksonInject(useInput = OptBoolean.FALSE)`
2. Add `Preconditions.checkState(config.isEnabled(), "JavaScript is disabled")` in constructors that don't already have it
## Exploit Payload Example
```json
{
"type": "index",
…Read the whole file at its exact version.
How to install
mdr add cxcscmu/skilllearnbench/druid-javascript-rce@sha256:c218c08f4ea728d0The line at the top of this page pins the label git:20260424.d50cf5a, 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_7sdujct67aqvmmt4)
2 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 1 version of this file, committed on Apr 24, 2026.
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 (1956 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
cxcscmu/skilllearnbench · 91 stars · license MIT · pushed 2026-10-02 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_7sdujct67aqvmmt4 GET https://markdownregistry.com/api/v1/resolve?ref=cxcscmu/skilllearnbench/druid-javascript-rce GET https://markdownregistry.com/api/v1/blob/c218c08f4ea728d0af4a20ba2e8b2f50f4df6ceb97f70233294959019d156fc7
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.