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


- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 23 Jan 2019
- **Updated:** 4 Aug 2024
- **Also known as:** ALPINE-CVE-2019-6706, ALSA-2019:3706, AZL-6669, DEBIAN-CVE-2019-6706, GHSA-f6gj-vrmg-ccf7, JLSEC-2026-553, RHSA-2019:3706, RLSA-2019:3706, SUSE-SU-2019:0247-1, UBUNTU-CVE-2019-6706, USN-3941-1, openSUSE-SU-2019:0175-1

## What is CVE-2019-6706?

CVE-2019-6706 is a high-severity vulnerability in Canonical Ubuntu Linux, published on 23 Jan 2019. 

### Official 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.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2019-6706?

It affects 2 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `lua` | AlmaLinux:8 | All versions | 5.3.4-11.el8 |
| `lua-devel` | AlmaLinux:8 | All versions | 5.3.4-11.el8 |
| `lua` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.3.4-11.el8 |
| `lua-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.3.4-11.el8 |
| `lua-debugsource` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.3.4-11.el8 |
| `lua-libs-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.3.4-11.el8 |
| `lua` | Red Hat:enterprise_linux:8::baseos | All versions | 0:5.3.4-11.el8 |
| `lua-debuginfo` | Red Hat:enterprise_linux:8::baseos | All versions | 0:5.3.4-11.el8 |
| `lua-debugsource` | Red Hat:enterprise_linux:8::baseos | All versions | 0:5.3.4-11.el8 |
| `lua-libs` | Red Hat:enterprise_linux:8::baseos | All versions | 0:5.3.4-11.el8 |
| `lua-libs-debuginfo` | Red Hat:enterprise_linux:8::baseos | All versions | 0:5.3.4-11.el8 |
| `lua` | Red Hat:enterprise_linux:8::crb | All versions | 0:5.3.4-11.el8 |
| `lua-debuginfo` | Red Hat:enterprise_linux:8::crb | All versions | 0:5.3.4-11.el8 |
| `lua-debugsource` | Red Hat:enterprise_linux:8::crb | All versions | 0:5.3.4-11.el8 |
| `lua-devel` | Red Hat:enterprise_linux:8::crb | All versions | 0:5.3.4-11.el8 |
| `lua-libs-debuginfo` | Red Hat:enterprise_linux:8::crb | All versions | 0:5.3.4-11.el8 |
| `lua` | Rocky Linux:8 | All versions | 0:5.3.4-11.el8 |
| `lua53` | SUSE:Linux Enterprise Module for Basesystem 15 | All versions | 5.3.4-3.3.2 |
| `lua53` | openSUSE:Leap 15.0 | All versions | 5.3.4-lp150.2.3.1 |

Products: Canonical Ubuntu Linux, Lua Lua.

## How do I fix CVE-2019-6706?

Upgrade to a fixed version.

## Is CVE-2019-6706 being exploited?

There is no known exploitation of CVE-2019-6706 in the wild and no public exploit code.

Public exploit code:

- Lua 5.3.5 - 'debug.upvaluejoin' Use After Free (exploitdb)

## Other vulnerabilities in Canonical Ubuntu Linux

- [CVE-2020-11651](https://insights.sbomify.com/CVE-2020-11651/): SaltStack Salt Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2020-7247](https://insights.sbomify.com/CVE-2020-7247/): OpenSMTPD Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2019-16928](https://insights.sbomify.com/CVE-2019-16928/): Exim Out-of-bounds Write (critical 9.8, exploited in the wild)
- [CVE-2018-6789](https://insights.sbomify.com/CVE-2018-6789/): Exim Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2015-2590](https://insights.sbomify.com/CVE-2015-2590/): Oracle Java SE and Java SE Embedded Remote Code Execution (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-6706 and fix it if it is affected.

What it is: CVE-2019-6706 is a high-severity vulnerability in Canonical Ubuntu Linux, published on 23 Jan 2019. 
Exploitation: There is no known exploitation of CVE-2019-6706 in the wild and no public exploit code.

Affected product: Canonical Ubuntu Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2019-6706/ (Markdown: https://insights.sbomify.com/CVE-2019-6706/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-6706
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-6706
- OSV: https://osv.dev/vulnerability/CVE-2019-6706

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-6706/
Summaries are generated and may contain mistakes; the official description above is the record.