GHSA-wf8f-6423-gfxg

### Overview

A flaw in Jackson-core's `JsonLocation._appendSourceDesc` method allows up to 500 bytes of unintended memory content to be included in exception messages. When parsing JSON from a byte array with an offset and length, the exception message incorrectly reads from the beginning of the array instead of the logical payload start. This results in possible **information disclosure** in systems using **pooled or reused buffers**, like Netty or Vert.x.

### Details

The vulnerability affects the creation of exception messages like:

``` JsonParseException: Unexpected character ... at [Source: (byte[])...] ```

When `JsonFactory.createParser(byte[] data, int offset, int len)` is used, and an error occurs while parsing, the exception message should include a snippet from the specified logical payload. However, the method `_appendSourceDesc` ignores the `offset`, and always starts reading from index `0`.

If the buffer contains residual sensitive data from a previous request, such as credentials or document contents, that data may be exposed if the exception is propagated to the client.

The issue particularly impacts server applications using:

* Pooled byte buffers (e.g., Netty) * Frameworks that surface parse errors in HTTP responses * Default Jackson settings (i.e., `INCLUDE_SOURCE_IN_LOCATION` is enabled)

A documented real-world example is [CVE-2021-22145](https://nvd.nist.gov/vuln/detail/CVE-2021-22145) in Elasticsearch, which stemmed from the same root cause.

### Attack Scenario

An attacker sends malformed JSON to a service using Jackson and pooled byte buffers (e.g., Netty-based HTTP servers). If the server reuses a buffer and includes the parser’s exception in its HTTP 400 response, the attacker may receive residual data from previous requests.

### Proof of Concept

```java byte[] buffer = new byte[1000]; System.arraycopy("SECRET".getBytes(), 0, buffer, 0, 6); System.arraycopy("{ \"bad\": }".getBytes(), 0, buffer, 700, 10);

JsonFactory factory = new JsonFactory(); JsonParser parser = factory.createParser(buffer, 700, 20); parser.nextToken(); // throws exception

// Exception message will include "SECRET" ```

### Patches This issue was silently fixed in jackson-core version 2.13.0, released on September 30, 2021, via [PR #652](https://github.com/FasterXML/jackson-core/pull/652).

All users should upgrade to version 2.13.0 or later.

### Workarounds If upgrading is not immediately possible, applications can mitigate the issue by:

1. **Disabling exception message exposure to clients** — avoid returning parsing exception messages in HTTP responses. 2. **Disabling source inclusion in exceptions** by setting:

```java jsonFactory.disable(JsonFactory.Feature.INCLUDE_SOURCE_IN_LOCATION); ```

This prevents Jackson from embedding any source content in exception messages, avoiding leakage.

### References * [Pull Request #652 (Fix implementation)](https://github.com/FasterXML/jackson-core/pull/652) * [CVE-2021-22145 (Elasticsearch exposure of this flaw)](https://nvd.nist.gov/vuln/detail/CVE-2021-22145)