NULL pointer dereference in Mrubyc
CVE-2026-86547
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.2 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.002 (7.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 8th percentile — 7.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000
Affected products
Weakness classification (CWE)
Public proof-of-concept exploits
References
- github.com/mrubyc/mrubyc/blob/4261cf5e5ae5579e3110dab98a04b91c7d919429/src/vm.c (technical-description)
- github.com/mrubyc/mrubyc/blob/release4.0.0/src/vm.c (technical-description)
- www.vulncheck.com/advisories/mrubyc-through-4.0.0-null-pointer-dereference-via-… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-86547?
- CVE-2026-86547 is a medium-severity vulnerability in Mrubyc, classified under NULL Pointer Dereference. CVSS score: 6.2/10. Published 2026-09-09.
- How severe is CVE-2026-86547?
- Medium severity. CVSS v3 base score is 6.2 out of 10.
- Is CVE-2026-86547 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.