Medium severity · published Sep 9, 2026
CVE-2026-86547
mrubyc through 4.0.0 NULL Pointer Dereference via OP_ENTER
6.2
CVSS
0.2%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Local
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 8% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MR
mrubyc · mrubyc
2.0 through 4.0.0 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-86547
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-86547
github.com
https://github.com/mrubyc/mrubyc/blob/4261cf5e5ae5579e3110dab98a04b91c7d919429/src/vm.c#L1534
github.com
https://github.com/mrubyc/mrubyc/blob/release4.0.0/src/vm.c#L1537
www.vulncheck.com
https://www.vulncheck.com/advisories/mrubyc-through-4.0.0-null-pointer-dereference-via-op-enter