CVE-2026-1979

mruby JMPNOT-to-JMPIF Optimization vm.c mrb_vm_exec use after free

State: Published
Severity: 4.8 Medium
Published: Feb 6, 2026
Updated: Feb 23, 2026
Reserved: Feb 5, 2026

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.

Scores

CVSS	Score	Vector	Source
4.0	4.8 Medium	CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P	VulDB
3.1	5.3 Medium	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L/E:P/RL:O/RC:C	VulDB
3.0	5.3 Medium	CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L/E:P/RL:O/RC:C	VulDB
2.0	4.3 Medium	AV:L/AC:L/Au:S/C:P/I:P/A:P/E:POC/RL:OF/RC:C	VulDB

Weaknesses

CWE-416 Use After Free
CWE-119 Memory Corruption

Affected Products

Product	Versions
mrubyn/a	3.0Affected 3.1Affected 3.2Affected 3.3Affected 3.4.0Affected

References

VDB-344501 | mruby JMPNOT-to-JMPIF Optimization vm.c mrb_vm_exec use after freevdb-entrytechnical-description
VDB-344501 | CTI Indicators (IOB, IOC, IOA)signaturepermissions-required
Submit #743377 | mruby cda2567 Use After Freethird-party-advisory
https://github.com/mruby/mruby/issues/6701issue-tracking
https://github.com/mruby/mruby/issues/6701#issue-3802609843exploitissue-tracking
https://github.com/sysfce2/mruby/commit/e50f15c1c6e131fa7934355eb02b8173b13df415patch
https://github.com/mruby/mruby/product

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