CVE-2026-1979

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

CVE-2026-1979 is fixed in mruby on 1 platform by DEBIAN-CVE-2026-1979 (version 4.0.0-1), released February 6, 2026. It is not reported as exploited. Patch Radar priority: Routine.

Routine

CVSS

5.5

Moderate

Exploitation

None reported

No vendor assessment

CISA KEV

Not listed

Not in the Known Exploited Vulnerabilities catalog

EPSS

0.0018

7th percentile

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.

Where it's fixed

Product	Fixed in	Fix	Released
Linux
mruby · Debian 14	4.0.0-1	DEBIAN-CVE-2026-1979	Feb 6, 2026

Details

Published
February 6, 2026
Weakness
Use After Free
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Vendor advisory
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-1979

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