# CVE-2026-86547

## Summary

- **CVE ID:** CVE-2026-86547
- **Severity:** MEDIUM
- **CVSS Score:** 6.9 (CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N)
- **CWE:** CWE-476
- **Published:** Sep 9, 2026
- **Last Modified:** Sep 9, 2026

## Description

mrubyc through 4.0.0 contains a null pointer dereference vulnerability in the op_enter() handler in src/vm.c when processing untrusted bytecode. Attackers can craft malicious .mrb bytecode files with OP_ENTER instructions at the top level to crash the embedding application and cause denial of service.

## Affected Products

- mrubyc — mrubyc (2.0)

## References

- [CNA](https://github.com/mrubyc/mrubyc/blob/release4.0.0/src/vm.c#L1537)
- [CNA](https://github.com/mrubyc/mrubyc/blob/4261cf5e5ae5579e3110dab98a04b91c7d919429/src/vm.c#L1534)
- [CNA](https://www.vulncheck.com/advisories/mrubyc-through-4.0.0-null-pointer-dereference-via-op-enter)

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-09._