CVE-2025-49128

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 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

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"

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:

   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)
• CVE-2021-22145 (Elasticsearch exposure of this flaw)

CVE-2025-49128 has a CVSS score of 4.0 (Medium). The vector is requires local access, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.13.0); upgrading removes the vulnerable code path.

Kodem intelligence

This issue was silently fixed in jackson-core version 2.13.0, released on September 30, 2021, via PR #652.

All users should upgrade to version 2.13.0 or later.

1. What is CVE-2025-49128? CVE-2025-49128 is a medium-severity security vulnerability in com.fasterxml.jackson.core:jackson-core (maven), affecting versions >= 2.0.0, < 2.13.0. It is fixed in 2.13.0.
2. How severe is CVE-2025-49128? CVE-2025-49128 has a CVSS score of 4.0 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of com.fasterxml.jackson.core:jackson-core are affected by CVE-2025-49128? com.fasterxml.jackson.core:jackson-core (maven) versions >= 2.0.0, < 2.13.0 is affected.
4. Is there a fix for CVE-2025-49128? Yes. CVE-2025-49128 is fixed in 2.13.0. Upgrade to this version or later.
5. Is CVE-2025-49128 exploitable, and should I be worried? Whether CVE-2025-49128 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2025-49128 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2025-49128? Upgrade com.fasterxml.jackson.core:jackson-core to 2.13.0 or later.