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