5.6

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2020-15366

CVE-2020-15366: Prototype Pollution in Ajv

An issue was discovered in ajv.validate() in Ajv (aka Another JSON Schema Validator) 6.12.2. A carefully crafted JSON schema could be provided that allows execution of other code by prototype pollution. (While untrusted schemas are recommended against, the worst case of an untrusted schema should be a denial of service, not execution of code.)

(GitHub Advisory)

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CVE-2020-15366

CVE-2020-15366:

5.6

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
ajv	npm	< 6.12.3	6.12.3

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability stemmed from insufficient type validation in schema processing functions. The patch adds number validation checks to these limit-related schema keywords (maximum, maxItems, etc.), which were previously vulnerable to prototype pollution when non-number values were provided. The commit diff shows added validation logic in these specific template files, and the test cases demonstrate how malicious schemas with string values in numeric fields could pass schema validation but trigger errors during compilation after the fix. These functions directly handle schema property validation and were missing critical type checks that enabled prototype pollution attacks.

Vulnerable functions

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WAF Protection Rules

WAF Rule

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Reasoning

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