Null Pointer Dereference Vulnerability in mrubyc by mruby
CVE-2026-86547

6.9MEDIUM

Key Information:

Vendor

Mrubyc

Status
Mrubyc
Vendor
CVE Published:
9 September 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2026-86547?

The mrubyc environment, in versions prior to 4.0.0, has a vulnerability that allows attackers to exploit a null pointer dereference in the op_enter() handler located in src/vm.c. By crafting malicious .mrb bytecode files with OP_ENTER instructions at the top level, an attacker could cause the embedded application to crash, resulting in a denial of service. This affects the stability and security of applications relying on mrubyc for bytecode execution.

Affected Version(s)

mrubyc 2.0 <= 4.0.0

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

cve-2026-86547-mrubyc-op-enter
Created by HarshRajSinghania

References

https://github.com/mrubyc/mrubyc/blob/release4.0.0/src/vm...
technical-description
https://github.com/mrubyc/mrubyc/blob/4261cf5e5ae5579e311...
technical-description
https://www.vulncheck.com/advisories/mrubyc-through-4.0.0...
third-party-advisory

CVSS V4

Score:
6.9
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
High
Attack Vector:
Local
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

Credit

Harsh Raj Singhania
.