CVE-2021-44964Public exploit

Sandbox escape via reentrant garbage collection

Published Mar 14, 2022 · Updated Aug 4, 2024

Use-after-free in Lua 5.4.0 through 5.4.3 allows attackers to escape an embedding application's sandbox via a crafted script. The lgc.c finalizer path permits a __gc metamethod to reenter the non-reentrant collector, leaving freed heap storage reusable and corruptible. The host must execute attacker-controlled Lua code with finalizers enabled; a public Linux exploit poisons tcache to replace __free_hook with system and launch a shell.

CVSS severity6.3
Medium
EPSS probability0.98%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Lua 5.4.0 through 5.4.3 allows attackers to escape an embedding application's sandbox via a crafted script. The lgc.c finalizer path permits a __gc metamethod to reenter the non-reentrant collector, leaving freed heap storage reusable and corruptible. The host must execute attacker-controlled Lua code with finalizers enabled; a public Linux exploit poisons tcache to replace __free_hook with system and launch a shell.

The record

CVE
CVE-2021-44964
Published
Mar 14, 2022
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-416, T1203
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 14, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.3GitLab Advisory DatabaseCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:N/I:N/A:H
6.3Oracle LinuxCVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:C/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-416Use After Free
T1203Exploitation for Client Execution

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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