Quick answers
- Is CVE-2026-38973 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-38973 being exploited in the wild.
- How severe is CVE-2026-38973?
- Informational severity, with a CVSS score of 0, published 6 July 2026.
- Which products and versions are affected?
- Mrubyc through 3.4.1.
- Is there a fix for CVE-2026-38973?
- 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-2026-38973 attacked?
- It is attacked with local access, in a software library.
- Am I affected by CVE-2026-38973?
- Check whether you run Mrubyc 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
An out-of-bounds read vulnerability exists in mrubyc through version 3.4.1 within the `mrbc_find_method()` function in `src/class.c`. The issue stems from improper boundary handling during a binary search of builtin method symbols, specifically where the `right` index was not correctly decremented relative to the number of builtin methods. An attacker capable of executing arbitrary Ruby code on the VM could trigger this out-of-bounds read during method lookup. This could result in a crash (denial of service) or information disclosure from the heap. A fix has been identified in commit f83a8b6 which correctly adjusts the search bounds.
Affected products
- mrubyc mrubyc through 3.4.1
Timeline
- 2026-07-06: disclosed
- 2026-07-06: advisory