What’s Vulnerable › Vulnerabilities

CVE-2026-86547: mrubyc through 4.0.0 NULL Pointer Dereference via OP_ENTER

• Severity: medium (CVSS 6.2 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-09 · updated 2026-09-10
• Weakness: CWE-476

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: from 2.0 through 4.0.0

References

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

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