CVE-2021-44964: Use after free in garbage collector and finalizer of lgc.c in Lua interpreter 5.4.0~5.4.3 allows attackers to

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MEDIUM 6.3UPGRADE

CVE-2021-44964 is a medium-severity flaw (CVSS 6.3) affecting lua. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Use after free in garbage collector and finalizer of lgc.c in Lua interpreter 5.4.0~5.4.3 allows attackers to perform Sandbox Escape via a crafted script file.

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	6.3 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	1.0% (top 38%)
CISA exploited list	No
Weakness	CWE-416
Published	2022-03-14
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: lua

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

Am I affected?

Timeline

2022-03-14 15:15 UTCPublished CVE record published
2026-06-17 04:13 UTCUpdated Record last modified

lua lua UPGRADE

Affected: >= 5.4.0 and <= 5.4.3

Fixed in: newer than 5.4.3

Safe to downgrade to: a release before 5.4.0

1. Check installed version

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

2. UPGRADE to newer than 5.4.3 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade lua

Note

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

3. If no update is available yet, DOWNGRADE to a release before 5.4.0 (Debian / Ubuntu)

apt-cache madison lua sudo apt install lua=<VERSION_BEFORE_5.4.0> sudo apt-mark hold lua

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list lua sudo dnf downgrade lua-<VERSION_BEFORE_5.4.0> sudo dnf versionlock add lua

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

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-2021-44964?

lua: upgrade to newer than 5.4.3. Exact commands for each OS are on this page.

Is CVE-2021-44964 being exploited?

CVE-2021-44964 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-2021-44964 affect?

CVE-2021-44964 affects lua. Severity is medium (CVSS 6.3). Use after free in garbage collector and finalizer of lgc.c in Lua interpreter 5.4.0~5.4.3 allows attackers to perform Sandbox Escape via a crafted script file.

How urgent is CVE-2021-44964?

Priority 43/100. Public exploit reference

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References

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