Description

Java: DoS Vulnerability in JSON-JAVA

Summary

A denial of service vulnerability in JSON-Java was discovered by ClusterFuzz. A bug in the parser means that an input string of modest size can lead to indefinite amounts of memory being used. There are two issues: (1) the parser bug can be used to circumvent a check that is supposed to prevent the key in a JSON object from itself being another JSON object; (2) if a key does end up being a JSON object then it gets converted into a string, using \ to escape special characters, including \ itself. So by nesting JSON objects, with a key that is a JSON object that has a key that is a JSON object, and so on, we can get an exponential number of \ characters in the escaped string.

Severity

High - Because this is an already-fixed DoS vulnerability, the only remaining impact possible is for existing binaries that have not been updated yet.

Proof of Concept

package orgjsonbug;

import org.json.JSONObject;

/**
 * Illustrates a bug in JSON-Java.
 */
public class Bug {...
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When run, this reports that the input string has length 367. Then, after a long pause, the program crashes inside new JSONObject with OutOfMemoryError.

Further Analysis

The issue is fixed by this PR.

Timeline

Date reported: 07/14/2023 Date fixed: Date disclosed: 10/12/2023

Mitigation

Aliases

References