java.lang.security.use-snakeyaml-constructor.use-snakeyaml-constructor

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Used SnakeYAML org.yaml.snakeyaml.Yaml() constructor with no arguments, which is vulnerable to deserialization attacks. Use the one-argument Yaml(...) constructor instead, with SafeConstructor or a custom Constructor as the argument.

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Defintion

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rules:
  - id: use-snakeyaml-constructor
    languages:
      - java
    metadata:
      owasp:
        - A08:2017 - Insecure Deserialization
        - A08:2021 - Software and Data Integrity Failures
      cwe:
        - "CWE-502: Deserialization of Untrusted Data"
      references:
        - https://securitylab.github.com/research/swagger-yaml-parser-vulnerability/#snakeyaml-deserialization-vulnerability
      category: security
      technology:
        - snakeyaml
      cwe2022-top25: true
      cwe2021-top25: true
      subcategory:
        - audit
      likelihood: LOW
      impact: HIGH
      confidence: LOW
      license: Commons Clause License Condition v1.0[LGPL-2.1-only]
    message: Used SnakeYAML org.yaml.snakeyaml.Yaml() constructor with no arguments,
      which is vulnerable to deserialization attacks. Use the one-argument
      Yaml(...) constructor instead, with SafeConstructor or a custom
      Constructor as the argument.
    patterns:
      - pattern: |
          $Y = new org.yaml.snakeyaml.Yaml();
          ...
          $Y.load(...);
    severity: WARNING

Examples

use-snakeyaml-constructor.java

import org.yaml.snakeyaml.Yaml;
import org.yaml.snakeyaml.constructor.SafeConstructor;

public class SnakeYamlTestCase {
    public void unsafeLoad(String toLoad) {
        // ruleid:use-snakeyaml-constructor
        Yaml yaml = new Yaml();
        yaml.load(toLoad);
    }

    public void safeConstructorLoad(String toLoad) {
        // ok:use-snakeyaml-constructor
        Yaml yaml = new Yaml(new SafeConstructor());
        yaml.load(toLoad);
    }

    public void customConstructorLoad(String toLoad, Class goodClass) {
        // ok:use-snakeyaml-constructor
        Yaml yaml = new Yaml(new Constructor(goodClass));
        yaml.load(toLoad);
    }
}