Medium severity · published Feb 6, 2026
CVE-2026-1979
mruby JMPNOT-to-JMPIF Optimization vm.c mrb_vm_exec use after free
5.5
CVSS
0.2%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 7% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MR
mruby · Mruby
3.0; 3.1; 3.2; 3.3; 3.4.0 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-1979
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-1979
Product
https://github.com/mruby/mruby/
Exploit
https://github.com/mruby/mruby/issues/6701
Exploit
https://github.com/mruby/mruby/issues/6701#issue-3802609843
Patch
https://github.com/sysfce2/mruby/commit/e50f15c1c6e131fa7934355eb02b8173b13df415
Permissions Required
https://vuldb.com/?ctiid.344501
Third Party Advisory
https://vuldb.com/?id.344501
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