Executive brief
mruby/c is a lightweight implementation of the Ruby programming language designed for microcontrollers and embedded systems with very limited memory. A technical flaw in how the software looks up internal functions could allow a specially crafted program to read data from memory locations it should not have access to. This could potentially lead to system instability or the exposure of sensitive information stored in the device's memory.
Technical details
An out-of-bounds read vulnerability exists in mrubyc through version 3.4.1 within the `mrbc_find_method()` function in `src/class.c`. The issue stems from improper boundary handling during a binary search of builtin method symbols, specifically where the `right` index was not correctly decremented relative to the number of builtin methods. An attacker capable of executing arbitrary Ruby code on the VM could trigger this out-of-bounds read during method lookup. This could result in a crash (denial of service) or information disclosure from the heap. A fix has been identified in commit f83a8b6 which correctly adjusts the search bounds.
Affected products
- mrubyc mrubyc through 3.4.1
Timeline
- 2026-07-06: disclosed
- 2026-07-06: advisory