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NVD / CVE Program· CNA mitre

CVE-2021-43519: Stack overflow in lua_resume of ldo.c in Lua Interpreter 5.1.0~5.4.4 allows attackers to perform a Denial of Service via a crafted script fi

Noroxi assessment

Priority: Monitor (action score 22/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 1.2% (FIRST EPSS); higher than 68.8% of all records.
  • Someone with local access to the system can trigger it. No account or password is required. A user must open a link or visit a page. No special conditions are required; it is repeatable.
  • Fixed version: lua (AlmaLinux:9) 5.4.4-2.el9_1; lua-devel (AlmaLinux:9) 5.4.4-2.el9_1; lua-libs (AlmaLinux:9) 5.4.4-2.el9_1.

Low priority for now. Upgrade to lua (AlmaLinux:9) 5.4.4-2.el9_1; lua-devel (AlmaLinux:9) 5.4.4-2.el9_1; lua-libs (AlmaLinux:9) 5.4.4-2.el9_1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

Stack overflow in lua_resume of ldo.c in Lua Interpreter 5.1.0~5.4.4 allows attackers to perform a Denial of Service via a crafted script file.

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
Nov 9, 2021
Updated
Jun 17, 2026
EPSS
1.2% · 68th percentile

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 1.2%

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
lualua
fedoraprojectfedora

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • fedoraproject fedora35
  • lua lua5.1.0 and later · before 5.3.5
  • lua lua5.4.0 and later · before 5.4.4

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:9luabefore 5.4.4-2.el9_15.4.4-2.el9_1
AlmaLinux:9lua-develbefore 5.4.4-2.el9_15.4.4-2.el9_1
AlmaLinux:9lua-libsbefore 5.4.4-2.el9_15.4.4-2.el9_1
Debian:12lua5.4before 5.4.4-15.4.4-1
openSUSE:Tumbleweedlua55before 5.5.0~beta1-1.15.5.0~beta1-1.1
Red Hat:enterprise_linux:9::appstreamluabefore 0:5.4.4-2.el9_10:5.4.4-2.el9_1
Red Hat:enterprise_linux:9::appstreamlua-debuginfobefore 0:5.4.4-2.el9_10:5.4.4-2.el9_1
Red Hat:enterprise_linux:9::appstreamlua-debugsourcebefore 0:5.4.4-2.el9_10:5.4.4-2.el9_1
Red Hat:enterprise_linux:9::appstreamlua-libs-debuginfobefore 0:5.4.4-2.el9_10:5.4.4-2.el9_1
Red Hat:enterprise_linux:9::baseoslua-libsbefore 0:5.4.4-2.el9_10:5.4.4-2.el9_1
Red Hat:enterprise_linux:9::crblua-develbefore 0:5.4.4-2.el9_10:5.4.4-2.el9_1
Red Hat:rhel_eus:9.0::appstreamluabefore 0:5.4.4-1.el9_0.10:5.4.4-1.el9_0.1
Red Hat:rhel_eus:9.0::appstreamlua-debuginfobefore 0:5.4.4-1.el9_0.10:5.4.4-1.el9_0.1
Red Hat:rhel_eus:9.0::appstreamlua-debugsourcebefore 0:5.4.4-1.el9_0.10:5.4.4-1.el9_0.1
Red Hat:rhel_eus:9.0::appstreamlua-libs-debuginfobefore 0:5.4.4-1.el9_0.10:5.4.4-1.el9_0.1
Red Hat:rhel_eus:9.0::baseoslua-libsbefore 0:5.4.4-1.el9_0.10:5.4.4-1.el9_0.1
Red Hat:rhel_eus:9.0::crblua-develbefore 0:5.4.4-1.el9_0.10:5.4.4-1.el9_0.1
Rocky Linux:9luabefore 0:5.4.4-2.el9_10:5.4.4-2.el9_1

Same product

lua: all records

Other highest-scoring records for the same primary product.

  • CVE-2020-15889Lua 5.4.0 has a getobjname heap-based buffer over-read because youngcollection in lgc.c uses markold for an insufficient number of list memb
    40Plan
  • CVE-2022-28805singlevar in lparser.c in Lua from (including) 5.4.0 up to (excluding) 5.4.4 lacks a certain luaK_exp2anyregup call, leading to a heap-based
    37Monitor
  • CVE-2020-15888Lua through 5.4.0 mishandles the interaction between stack resizes and garbage collection, leading to a heap-based buffer overflow, heap-bas
    36Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2020-24370Aug 17, 2020 · ldebug.c in Lua 5.4.0 allows a negation overflow and segmentation fault in getlocal and setlocal, as demonstrated by getlocal(3,2^31).
    22Monitor
  • ← EarlierCVE-2020-24371Aug 17, 2020 · lgc.c in Lua 5.4.0 mishandles the interaction between barriers and the sweep phase, leading to a memory access violation involving collectga
    22Monitor
  • Later →CVE-2021-44647Jan 11, 2022 · 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 servi
    22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
almalinux:lua5.4.4-2.el9_1 · AlmaLinux:9Package registry (OSV)
almalinux:lua-devel5.4.4-2.el9_1 · AlmaLinux:9Package registry (OSV)
almalinux:lua-libs5.4.4-2.el9_1 · AlmaLinux:9Package registry (OSV)
debian:lua5.45.4.4-1 · Debian:12Package registry (OSV)
opensuse:lua555.5.0~beta1-1.1 · openSUSE:TumbleweedPackage registry (OSV)
red hat:lua0:5.4.4-2.el9_1 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:lua-debuginfo0:5.4.4-2.el9_1 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:lua-debugsource0:5.4.4-2.el9_1 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:lua-devel0:5.4.4-2.el9_1 · Red Hat:enterprise_linux:9::crbPackage registry (OSV)
red hat:lua-libs0:5.4.4-2.el9_1 · Red Hat:enterprise_linux:9::baseosPackage registry (OSV)
red hat:lua-libs-debuginfo0:5.4.4-2.el9_1 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
rocky linux:lua0:5.4.4-2.el9_1 · Rocky Linux:9Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • No account or password is required.
  • A user must open a link or visit a page.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-674 · Uncontrolled Recursion

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (2 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records