# CVE-2026-40612: jqlang jq uncontrolled recursion in jv_contains

Source: https://junglewise.ai/threats/cve-2026-40612-jqlang-jq-uncontrolled-recursion-in-jv-contains  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-11. Updated: 2026-05-14  
License: CC BY 4.0 with a link back

CVE-2026-40612 · Severity: medium · CVSS 5.5 · Published 2026-05-11

jq is a widely used command-line tool and library for processing JSON data. A vulnerability in how it handles deeply nested data structures can cause the application to crash or potentially corrupt memory. This could lead to a denial-of-service or, in specific embedded environments, allow an attacker to interfere with other running processes or data.

Technologies: [Jqlang Jq](https://junglewise.ai/threats/technologies/jq). Vendors: [Jqlang](https://junglewise.ai/threats/vendors/jqlang).

## Quick answers

**Is CVE-2026-40612 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-40612 being exploited in the wild.

**How severe is CVE-2026-40612?** Medium severity, with a CVSS score of 5.5, published 11 May 2026.

**Which products and versions are affected?** Jqlang Jq <= 1.8.1.

**Is there a fix for CVE-2026-40612?** 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-2026-40612 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-40612?** Check whether you run Jqlang Jq 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 an uncontrolled recursion (CWE-674) within the jv_contains function in src/jv.c. While the standard JSON parser limits depth to 10,000, an attacker can programmatically construct more deeply nested structures using the 'reduce' function. When jq attempts to process these structures via the 'contains()' or 'inside()' functions, it exhausts the C stack. On standard Linux systems, this results in a SIGSEGV (Denial of Service); however, on systems without stack guard pages or where libjq is embedded in multi-threaded applications, this can lead to heap metadata corruption or adjacent thread stack overwrites. No patch was available at the time of the advisory.

## Affected products

- jqlang jq <= 1.8.1

## Timeline

- 2026-04-24: advisory: GitHub Security Advisory published
- 2026-05-11: disclosed: CVE-2026-40612 published to NVD

## References

- [https://github.com/jqlang/jq/security/advisories/GHSA-r7m6-x9c7-h69j](https://github.com/jqlang/jq/security/advisories/GHSA-r7m6-x9c7-h69j)

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