# CVE-2026-114129: stream-json FlexAssembler quadratic CPU consumption via nested JSON

Source: https://junglewise.ai/threats/cve-2026-114129-stream-json-is-a-micro-library-of-stream-components-for  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-21. Updated: 2026-10-21  
License: CC BY 4.0 with a link back

CVE-2026-114129 · Severity: medium · CVSS 6.2 · Published 2026-10-21

stream-json is a library for parsing JSON and JSONC documents with minimal memory overhead. In versions 2.0.0 through 3.6.x, deeply nested documents can cause the FlexAssembler component to consume CPU quadratically, stalling all concurrent operations in a process. An attacker can exploit this by sending a crafted malicious JSON document, causing a denial of service.

Technologies: [stream-json (npm)](https://junglewise.ai/threats/technologies/stream-json). Vendors: [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is CVE-2026-114129 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-114129 being exploited in the wild.

**How severe is CVE-2026-114129?** Medium severity, with a CVSS score of 6.2, published 21 October 2026.

**Which products and versions are affected?** stream-json (npm) >= 2.0.0, <= 3.6.0, SEMVER:introduced=2.0.0,fixed=3.7.0; Stream-Json 2.0.0 to 3.6.x.

**Is there a fix for CVE-2026-114129?** Yes. stream-json (npm): upgrade to 3.7.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-114129 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-114129?** Check whether you run stream-json (npm) or Stream-Json 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.

## How to fix

- stream-json (npm): upgrade to 3.7.0 or later

  ```sh
  npm install stream-json@3.7.0
  ```


## Technical details

The vulnerability exists in FlexAssembler's compilation of string and regular-expression path filters: on every container start, it joins the full key stack regardless of nesting depth, causing O(D²) CPU consumption for documents nested to depth D. The join occurs before rule matching, so no schema knowledge is required. Single-threaded Node.js event loops become stalled; applications using only function filters or no rules are unaffected. The fix in 3.7.0 adds depth capping.

## Affected products

- stream-json stream-json 2.0.0 to 3.6.x

## Identifiers

- CVE-2026-114129
- GHSA-jj87-hc4r-jwfw

## Timeline

- 2026-10-21: disclosed
- 2026-09-19: patched: Fix committed to repository

## References

- [https://github.com/uhop/stream-json/commit/1929fd80495d45b47e8f8cb1d4e132f915aef012](https://github.com/uhop/stream-json/commit/1929fd80495d45b47e8f8cb1d4e132f915aef012)
- [https://github.com/uhop/stream-json/commit/c06c9a3c02adef89543e26ecebb45837cb284512](https://github.com/uhop/stream-json/commit/c06c9a3c02adef89543e26ecebb45837cb284512)

## Related threats

- [stream-json prototype pollution via __proto__ key](https://junglewise.ai/threats/cve-2026-104183-stream-json-is-a-micro-library-of-stream-components-for)
- [stream-json JSONC parser ReDoS in comment handling](https://junglewise.ai/threats/cve-2026-104182-stream-json-is-a-micro-library-of-stream-components-for)
- [stream-json path filters algorithmic complexity denial of service](https://junglewise.ai/threats/cve-2026-71429-stream-json-path-filters-algorithmic-complexity-denial-of-service)