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

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MEDIUM

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

Published Feb 6, 2026

4.8

MEDIUM

CVSS 4.0

EPSS 0.18%

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

Vendor Mruby Product Mruby Default
n/a
- Version
  3.0
  Status
  affected
  Constraints
  -
- Version
  3.1
  Status
  affected
  Constraints
  -
- Version
  3.2
  Status
  affected
  Constraints
  -
- Version
  3.3
  Status
  affected
  Constraints
  -
- Version
  3.4.0
  Status
  affected
  Constraints
  -

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor

Product

Default status

Versions

Mruby

n/a

Version	Status	Constraints
3.0	affected	-
3.1	affected	-
3.2	affected	-
3.3	affected	-
3.4.0	affected	-

Remediation

No remediation recorded yet.

Weaknesses (2)

CWE-119

Buffer Overflow

CWE-416

Use After Free

References (7)

https://github.com/mruby/mruby/
product
https://github.com/mruby/mruby/issues/6701
issue-trackingExploitIssue Tracking
https://github.com/mruby/mruby/issues/6701#issue-3802609843
exploitissue-trackingIssue Tracking
https://github.com/sysfce2/mruby/commit/e50f15c1c6e131fa7934355eb02b8173b13df415
patch
https://vuldb.com/?ctiid.344501
signaturepermissions-requiredPermissions RequiredVDB Entry
https://vuldb.com/?id.344501
vdb-entrytechnical-descriptionThird Party AdvisoryVDB Entry
https://vuldb.com/?submit.743377
third-party-advisoryThird Party AdvisoryVDB Entry

Link	Providers	Tags
https://github.com/mruby/mruby/		product
https://github.com/mruby/mruby/issues/6701		issue-trackingExploitIssue Tracking
https://github.com/mruby/mruby/issues/6701#issue-3802609843		exploitissue-trackingIssue Tracking
https://github.com/sysfce2/mruby/commit/e50f15c1c6e131fa7934355eb02b8173b13df415		patch
https://vuldb.com/?ctiid.344501		signaturepermissions-requiredPermissions RequiredVDB Entry
https://vuldb.com/?id.344501		vdb-entrytechnical-descriptionThird Party AdvisoryVDB Entry
https://vuldb.com/?submit.743377		third-party-advisoryThird Party AdvisoryVDB Entry