# CVE-2026-86318: java-json-tools json-patch stack overflow in merge patch deserialization

Source: https://junglewise.ai/threats/cve-2026-86318-java-json-tools-json-patch-stack-overflow-in-merge-patch  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-07. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-86318 · Severity: medium · CVSS 5.3 · Published 2026-09-07

java-json-tools json-patch is a Java library that implements JSON Patch and JSON Merge Patch standards. A flaw in the JsonMergePatch deserialization allows attackers to send deeply nested JSON objects that cause the application to crash with a StackOverflowError, disrupting service availability. This requires no authentication and can be exploited with a single malicious HTTP request.

## Quick answers

**Is CVE-2026-86318 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-86318 being exploited in the wild.

**How severe is CVE-2026-86318?** Medium severity, with a CVSS score of 5.3, published 7 September 2026.

**Which products and versions are affected?** java-json-tools json-patch up to 1.13.

**Is there a fix for CVE-2026-86318?** 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 CVE-2026-86318 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-86318?** Check whether anything you run is named in the advisory. 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 an uncontrolled recursion flaw in JsonMergePatchDeserializer.deserialize() (CWE-674). When processing nested JSON objects, the deserializer recursively calls itself without any depth limit. An attacker can craft a JSON structure with 2000+ nesting levels to trigger a StackOverflowError that kills the processing thread and cannot be reliably caught. The attack vector is network-based (remote) with no authentication or user interaction required. The flaw exists regardless of Jackson's own parsing depth protections, because it affects json-patch's custom deserialization logic applied to already-parsed JsonNode objects. The project has not yet released a patch.

## Affected products

- java-json-tools json-patch up to 1.13

## Timeline

- 2026-07-29: disclosed: Security issue reported on GitHub
- 2026-09-07: other: CVE-2026-86318 published

## References

- [https://github.com/java-json-tools/json-patch/](https://github.com/java-json-tools/json-patch/)
- [https://github.com/java-json-tools/json-patch/issues/168](https://github.com/java-json-tools/json-patch/issues/168)