Quick answers
- Is CVE-2026-86547 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-86547 being exploited in the wild.
- How severe is CVE-2026-86547?
- Medium severity, with a CVSS score of 6.2, published 9 September 2026.
- Which products and versions are affected?
- Mrubyc through 4.0.0.
- Is there a fix for CVE-2026-86547?
- 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-2026-86547 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-86547?
- 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
A null pointer dereference vulnerability exists in the op_enter() handler within src/vm.c when processing OP_ENTER instructions in untrusted bytecode. Attackers can craft malicious .mrb bytecode files that place OP_ENTER instructions at the top level (outside of function/method definitions) to trigger the null dereference, crashing the embedding application. The vulnerability is triggered when bytecode is loaded and executed; no authentication or special privileges are required. An attacker can achieve denial of service by causing the application to crash, but code execution is not directly possible from this vulnerability alone.
Affected products
- mrubyc mrubyc through 4.0.0
Timeline
- 2026-09-09: disclosed