# FasterXML jackson-core memory exhaustion in async parser via chunked digits

Source: https://junglewise.ai/threats/fasterxml-jackson-core-memory-exhaustion-in-async-parser-via-chunked-aac0fe2a  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-21. Updated: 2026-07-21  
License: CC BY 4.0 with a link back

Severity: high · CVSS 8.7 · Published 2026-07-21

Jackson-core is a widely used Java library for processing JSON data, often utilized by web frameworks like Spring WebFlux and Quarkus. A flaw in its asynchronous data parser allows an attacker to send specially crafted, extremely long numbers in small chunks to exhaust a server's memory. This can lead to a denial-of-service (DoS) condition where the application crashes or becomes unresponsive, even if administrators have set limits on maximum number lengths.

Technologies: [FasterXML Jackson-Core](https://junglewise.ai/threats/technologies/jackson-core). Vendors: [FasterXML](https://junglewise.ai/threats/vendors/fasterxml).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** High severity, with a CVSS score of 8.7, published 21 July 2026.

**Which products and versions are affected?** FasterXML Jackson-Core >= 3.0.0, < 3.1.4, >= 3.2.0, < 3.2.1.

**Is there a fix for This vulnerability?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is This vulnerability attacked?** It is attacked over the network, in a software library.

**Am I affected?** Check whether you run FasterXML Jackson-Core at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is a resource exhaustion issue (CWE-770) in `NonBlockingUtf8JsonParserBase.java`. While a previous fix (GHSA-72hv-8253-57qq) added length validation when a number is completed, it failed to validate the length of the internal `TextBuffer` when the parser returns `NOT_AVAILABLE` during chunked input. An attacker can stream a continuous sequence of digits without a terminator, causing the buffer to expand up to the `maxStringLength` (default 20MB) instead of being capped by `maxNumberLength` (default 1000). This allows for significant memory amplification per connection. The issue specifically affects reactive/non-blocking stacks using `JsonFactory.createNonBlockingByteArrayParser()`. Patches are available in versions 2.18.8, 2.21.4, 2.22.1, 3.1.4, and 3.2.1.

## Affected products

- FasterXML jackson-core < 2.18.8, >= 2.19.0, < 2.21.4, >= 2.22.0, < 2.22.1
- tools.jackson.core jackson-core >= 3.0.0, < 3.1.4, >= 3.2.0, < 3.2.1

## Timeline

- 2026-02-28: other: Parent advisory GHSA-72hv-8253-57qq published
- 2026-07-10: advisory: GitHub Advisory published
- 2026-07-21: disclosed: Full technical details and PoC disclosed

## References

- [https://api.github.com/users/tonghuaroot](https://api.github.com/users/tonghuaroot)
- [https://github.com/tonghuaroot](https://github.com/tonghuaroot)
- [https://api.github.com/users/tonghuaroot/gists%7B/gist_id%7D](https://api.github.com/users/tonghuaroot/gists%7B/gist_id%7D)
- [https://api.github.com/users/tonghuaroot/repos](https://api.github.com/users/tonghuaroot/repos)
- [https://avatars.githubusercontent.com/u/23011166?v=4](https://avatars.githubusercontent.com/u/23011166?v=4)
- [https://api.github.com/users/tonghuaroot/events%7B/privacy%7D](https://api.github.com/users/tonghuaroot/events%7B/privacy%7D)

## Related threats

- [Jackson Core denial of service via unbounded JSON property name allocation](https://junglewise.ai/threats/cve-2026-68498-streamreadconstraints-maxnamelength-default-50-000-characters-is)
- [FasterXML jackson-core denial of service in UTF8DataInputJsonParser](https://junglewise.ai/threats/cve-2026-89425-utf8datainputjsonparser-reportinvalidtoken-in-fasterxml-jackson)
- [FasterXML jackson-core regular expression denial of service in NumberInput](https://junglewise.ai/threats/cve-2026-89407-numberinput-lookslikevalidnumber-in-fasterxml-jackson-core-pre)
- [FasterXML jackson-core number length constraint bypass in async parser](https://junglewise.ai/threats/fasterxml-jackson-core-number-length-constraint-bypass-in-async-parser-78aa3f75)
- [FasterXML jackson-core incomplete number length validation bypass](https://junglewise.ai/threats/cve-2026-68494-fasterxml-jackson-core-incomplete-number-length-validation-bypass)