What is evo-druid-cve-patch?

A security patch for Apache Druid 0.20.0 addressing CVE-2021-25646, a flaw that can enable code execution through specially formed JSON requests. It validates request data and hardens Jackson-based configuration handling.

Use it to patch the affected Druid Java code and reject the described malicious request pattern.

It blocks empty JSON keys that can override a server setting and lead to unsafe JavaScript execution. The changes provide both request checking and additional configuration protection.

evo-druid-cve-patch — Skill for Claude Code and Codex by OpenLAIR

Install

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.

Any agent

npx skills add OpenLAIR/OpenSkill --skill evo-druid-cve-patch

Clone the repo

git clone --depth 1 https://github.com/OpenLAIR/OpenSkill

Made for: Claude Code, Codex.

Wrote 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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/openlair/openskill/evo-druid-cve-patch/github.svg)](https://agentmods.dev/skills/openlair/openskill/evo-druid-cve-patch)

Your own site

<a href="https://agentmods.dev/skills/openlair/openskill/evo-druid-cve-patch"><img src="https://agentmods.dev/badge/skills/openlair/openskill/evo-druid-cve-patch/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/openlair/openskill/evo-druid-cve-patch"><img src="https://agentmods.dev/badge/skills/openlair/openskill/evo-druid-cve-patch.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 56 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 815 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

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	$0.00056	$0.00815
Opus 5	$0.00028	$0.00407
Sonnet 5	$0.00011	$0.00163
Haiku 4.5	$0.00006	$0.00081

Measured yesterday against content hash 65ea471704f3, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

evo-druid-cve-patch scanned grade A with 0 findings 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 yesterday.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/patch_druid.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

tasks-evolved/fix-druid-loophole-cve/environment/skills/evo-druid-cve-patch/SKILL.md · 79 lines

How it starts

The opening of the file, as written. The whole thing — 79 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Skill: evo-druid-cve-patch

Purpose

Patches Apache Druid 0.20.0 for CVE-2021-25646 - a JavaScript injection vulnerability where empty-string keys in JSON payloads can override server-side JavaScriptConfig to enable arbitrary code execution.

Vulnerability Summary

CVE: CVE-2021-25646
Affected: Apache Druid <= 0.20.0
Mechanism: Empty key "" in JSON overrides @JacksonInject JavaScriptConfig parameter
Impact: Authenticated RCE via JavaScript filters/aggregators/extraction functions

Patch Strategy (Two-Layer Defense)

Layer 1: Raw JSON Validation (SamplerResource - Approach 3)

Modify SamplerResource.java to:

Accept raw String instead of auto-deserialized SamplerSpec
Check for empty-string key pattern (""\s*:) using regex
Reject requests containing empty keys with 400 Bad Request
Only then deserialize via ObjectMapper.readValue()

Requires injecting @Json ObjectMapper via Guice constructor injection. Return type changes from SamplerResponse to Response for error handling.

Layer 2: Jackson Injection Hardening (Approach 2 - Defense in Depth)

Add @JacksonInject(useInput = OptBoolean.FALSE) to all three JavaScript classes:

JavaScriptDimFilter (processing module)
JavaScriptAggregatorFactory (processing module)
JavaScriptExtractionFn (processing module)

This tells Jackson 2.9+ to never populate the JavaScriptConfig parameter from JSON input.

Affected Files

indexing-service/src/main/java/org/apache/druid/indexing/overlord/sampler/SamplerResource.java
processing/src/main/java/org/apache/druid/query/filter/JavaScriptDimFilter.java
processing/src/main/java/org/apache/druid/query/aggregation/JavaScriptAggregatorFactory.java
processing/src/main/java/org/apache/druid/query/extraction/JavaScriptExtractionFn.java

Usage

import sys
sys.path.insert(0, '/app/environment/skills/evo-druid-cve-patch/scripts')
from patch_druid import apply_all_patches, generate_patch_file, run_maven_build

# Apply patches to source
apply_all_patches('/root/druid')

# Generate patch file
generate_patch_file('/root/druid', '/root/patches/fix-cve-2021-25646.patch')

# Build
run_maven_build('/root/druid')

Read the full file on GitHub · 79 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

scripts/patch_druid.py 7.7 KB runs code

Changes

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.

yesterday First seen · 79 lines · 56 tokens per session scan A 65ea471704f3

Subscribe to this mod's changes

evo-druid-cve-patch is a skill published in the GitHub repository OpenLAIR/OpenSkill (90 stars, last pushed yesterday), licensed Apache-2.0. It adds 56 tokens to every session and 815 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-11.

Java Languages Security agent-skills ai-agents llm-agents open world self-evolving-agents

evo-druid-cve-patch

Getting it into your agent

Wrote this? Show the measurements

What it costs to keep this loaded

Grade A, and why

Nothing flagged

How it starts

Skill: evo-druid-cve-patch

Purpose

Vulnerability Summary

Patch Strategy (Two-Layer Defense)

Layer 1: Raw JSON Validation (SamplerResource - Approach 3)

Layer 2: Jackson Injection Hardening (Approach 2 - Defense in Depth)

Affected Files

Usage

What ships with it

What this file has done since we first saw it

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