Quick answers
- Is CVE-2026-120440 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-120440 being exploited in the wild.
- How severe is CVE-2026-120440?
- Medium severity, with a CVSS score of 5.3, published 2 November 2026.
- Which products and versions are affected?
- QuickJS-NG before 0.16.0.
- Is there a fix for CVE-2026-120440?
- Yes: fixed in 0.16.0. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-120440 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-120440?
- Check whether you run QuickJS-NG 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
- Fixed in: 0.16.0
Technical details
A memory leak exists in the js_atomics_store() function in quickjs.c: when Atomics.store() returns a RangeError due to a detached or resized typed array buffer, it fails to free a previously converted value, allowing attackers to trigger repeated allocations. The vulnerability requires JavaScript execution context and can be exploited via malicious script code that calls Atomics.store with a valueOf trap that modifies the underlying buffer.
Affected products
- QuickJS-NG QuickJS-NG before 0.16.0
Timeline
- 2026-11-02: disclosed