CVE-2026-1979: mruby JMPNOT-to-JMPIF Optimization vm.c mrb_vm_exec use after free

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-02-06 · updated 2026-06-17
Weakness: CWE-119

Description

A flaw has been found in mruby up to 3.4.0. This affects the function mrb_vm_exec of the file src/vm.c of the component JMPNOT-to-JMPIF Optimization. Executing a manipulation can lead to use after free. The attack needs to be launched locally. The exploit has been published and may be used. This patch is called e50f15c1c6e131fa7934355eb02b8173b13df415. It is advisable to implement a patch to correct this issue.

Affected products

mruby/mruby: through 3.4.0

References

https://github.com/mruby/mruby/
https://github.com/mruby/mruby/issues/6701
https://github.com/mruby/mruby/issues/6701#issue-3802609843
https://github.com/sysfce2/mruby/commit/e50f15c1c6e131fa7934355eb02b8173b13df415
https://vuldb.com/?ctiid.344501
https://vuldb.com/?id.344501
https://vuldb.com/?submit.743377

Get alerted when CVE-2026-1979 or the next vulnerability affects your stack