# CVE-2026-38976: mrubyc NULL pointer dereference in op_super

Source: https://junglewise.ai/threats/cve-2026-38976-mrubyc-null-pointer-dereference-in-op-super  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-06. Updated: 2026-07-06  
License: CC BY 4.0 with a link back

CVE-2026-38976 · Severity: info · Published 2026-07-06

mruby/c is a lightweight implementation of the Ruby programming language designed for microcontrollers and embedded systems with limited memory. A vulnerability was found where the software crashes when it encounters a 'super' command used in an improper context, such as at the top level of a script. This allows a specially crafted program to shut down the interpreter, potentially causing a denial-of-service for the device or application using it.

Technologies: [Mrubyc](https://junglewise.ai/threats/technologies/mrubyc). Vendors: [Mrubyc](https://junglewise.ai/threats/vendors/mrubyc).

## Quick answers

**Is CVE-2026-38976 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-38976 being exploited in the wild.

**How severe is CVE-2026-38976?** Informational severity, published 6 July 2026.

**Which products and versions are affected?** Mrubyc through 3.4.1.

**Is there a fix for CVE-2026-38976?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-38976 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-38976?** Check whether you run Mrubyc at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A NULL pointer dereference exists in src/vm.c within the op_super() function (OP_SUPER opcode). The vulnerability is caused by a missing runtime guard when 'super' is called at the top-level or outside of a method context, where vm->callinfo_tail is NULL. An attacker who can provide or execute arbitrary mruby bytecode (.mrb files) can trigger this dereference, leading to a process crash (Denial of Service). This issue is similar to CVE-2022-1201 in the main mruby implementation. A fix has been identified that adds a check for NULL callinfo and raises a NoMethodError instead of crashing.

## Affected products

- mrubyc mrubyc through 3.4.1

## Timeline

- 2026-03-19: disclosed: Issue reported on GitHub
- 2026-07-06: advisory: CVE published to NVD

## References

- [https://github.com/hayat01sh1da/mrubyc/commit/c4aa2a06bfdd13a0f1ae5165c5760a2530314a42](https://github.com/hayat01sh1da/mrubyc/commit/c4aa2a06bfdd13a0f1ae5165c5760a2530314a42)
- [https://github.com/mrubyc/mrubyc](https://github.com/mrubyc/mrubyc)
- [https://github.com/mrubyc/mrubyc/issues/276](https://github.com/mrubyc/mrubyc/issues/276)

## Related threats

- [mrubyc null pointer dereference in op_enter handler](https://junglewise.ai/threats/cve-2026-86547-mrubyc-null-pointer-dereference-in-op-enter-handler)
- [mrubyc out-of-bounds read in mrbc_find_method](https://junglewise.ai/threats/cve-2026-38973-mrubyc-out-of-bounds-read-in-mrbc-find-method)