CVE-2026-1979: A flaw has been found in mruby up to 3.4.0

Q: How do I fix CVE-2026-1979?

mruby: upgrade to newer than 3.4.0. Exact commands for each OS are on this page.

Q: Is CVE-2026-1979 being exploited?

CVE-2026-1979 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-1979 affect?

CVE-2026-1979 affects mruby. Severity is medium (CVSS 5.3). 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 local

Q: How urgent is CVE-2026-1979?

Priority 25/100. Public exploit reference

Routine

MEDIUM 5.3UPGRADE

CVE-2026-1979 is a medium-severity flaw (CVSS 5.3) affecting mruby. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.2% (top 93%)
CISA exploited list	No
Weakness	CWE-119, CWE-416
Published	2026-02-06
Last modified	2026-06-17

Publisher (CNA): VulDB · Vendor: mruby

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-02-06 05:16 UTCPublished CVE record published
2026-06-17 10:16 UTCUpdated Record last modified

mruby mruby UPGRADE

Affected: <= 3.4.0

Fixed in: newer than 3.4.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy mruby || rpm -q mruby || mruby --version

2. UPGRADE to newer than 3.4.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade mruby

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade mruby

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-1979?

mruby: upgrade to newer than 3.4.0. Exact commands for each OS are on this page.

Is CVE-2026-1979 being exploited?

CVE-2026-1979 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-1979 affect?

CVE-2026-1979 affects mruby. Severity is medium (CVSS 5.3). 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 local

How urgent is CVE-2026-1979?

Priority 25/100. Public exploit reference

Related CVEs

CVE-2025-13120 MEDIUM 5.3 UPGRADE A vulnerability has been found in mruby up to 3.4.0
CVE-2025-12875 MEDIUM 5.3 DOWNGRADE A weakness has been identified in mruby 3.4.0
CVE-2025-7207 LOW 3.3 UPGRADE A vulnerability, which was classified as problematic, was found in mruby up to 3.4.0-rc2

References

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