CVE-2021-44647: Lua v5.4.3 and above are affected by SEGV by type confusion in funcnamefromcode function in ldebug.c which can

Routine

MEDIUM 5.5DOWNGRADEMITIGATE

CVE-2021-44647 is a medium-severity flaw (CVSS 5.5) affecting lua, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Lua v5.4.3 and above are affected by SEGV by type confusion in funcnamefromcode function in ldebug.c which can cause a local denial of service.

Why this priority

Public exploit reference

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	5.5 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.4% (top 64%)
CISA exploited list	No
Weakness	CWE-843
Published	2022-01-11
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: fedoraproject · lua

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

Am I affected?

Timeline

2022-01-11 13:15 UTCPublished CVE record published
2026-06-17 04:12 UTCUpdated Record last modified

lua lua DOWNGRADE

Affected: 5.4.3

Fixed in: no fixed release known

Safe to downgrade to: a release before 5.4.3

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 5.4.3 (Debian / Ubuntu)

apt-cache madison lua sudo apt install lua=<VERSION_BEFORE_5.4.3> sudo apt-mark hold lua

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list lua sudo dnf downgrade lua-<VERSION_BEFORE_5.4.3> 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.

fedoraproject fedora MITIGATE

Affected: 34

Fixed in: no fixed release known

Safe to downgrade to: a release before 34

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

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-2021-44647?

lua: downgrade or apply the listed mitigation; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-44647 being exploited?

CVE-2021-44647 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-2021-44647 affect?

CVE-2021-44647 affects lua, fedora. Severity is medium (CVSS 5.5). Lua v5.4.3 and above are affected by SEGV by type confusion in funcnamefromcode function in ldebug.c which can cause a local denial of service.

How urgent is CVE-2021-44647?

Priority 33/100. Public exploit reference

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References

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