CVE-2026-86547

Application crash via top-level OP_ENTER instruction

Published Sep 9, 2026 · Updated Sep 9, 2026

Null pointer dereference in mruby/c 2.0 through 4.0.0 allows attackers to crash an embedding application via crafted .mrb bytecode. The op_enter() handler in src/vm.c fails to reject an OP_ENTER instruction at bytecode top level and consequently dereferences a null pointer. Attackers must place untrusted bytecode where an embedding application processes it; exploitation terminates that application without disclosing or modifying data.

CVSS severity6.9
Medium
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Null pointer dereference in mruby/c 2.0 through 4.0.0 allows attackers to crash an embedding application via crafted .mrb bytecode. The op_enter() handler in src/vm.c fails to reject an OP_ENTER instruction at bytecode top level and consequently dereferences a null pointer. Attackers must place untrusted bytecode where an embedding application processes it; exploitation terminates that application without disclosing or modifying data.

The record

CVE
CVE-2026-86547
Published
Sep 9, 2026
Updated
Sep 9, 2026
Vendor
ITOC mruby/c team
Product
mruby/c
Classifications
CWE-476, T1499.004
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.0 <=4.0.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

ITOC mruby/c team · mruby/cversion=2.0 <=4.0.0

Published CVSS scores

6.2VulnCheck CNACVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
6.9VulnCheck CNACVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo