# CVE-2023-39320: Arbitrary code execution via go.mod toolchain directive in cmd/go

> Attackers can execute arbitrary code by exploiting the go.mod toolchain directive when running the go command within a module.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 8 Sep 2023
- **Updated:** 13 Feb 2025
- **Also known as:** BELL-CVE-2023-39320, BIT-golang-2023-39320, GHSA-rxv8-v965-v333, GO-2023-2042

## What is CVE-2023-39320?

CVE-2023-39320 is a critical code injection vulnerability in Golang Go, published on 8 Sep 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The go.mod toolchain directive, introduced in Go 1.21, can be leveraged to execute scripts and binaries relative to the root of the module when the "go" command was executed within the module. This applies to modules downloaded using the "go" command from the module proxy, as well as modules downloaded directly using VCS software.

Weakness: CWE-94 (Improper Control of Generation of Code)

## Which versions are affected by CVE-2023-39320?

2 open source packages ship an affected version, including golang and toolchain. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `golang` | Bitnami | From 1.21.0 | 1.21.1 |
| `toolchain` | Go | From 1.21.0-0 | 1.21.1 |

Products: Golang Go.

## How do I fix CVE-2023-39320?

Upgrade golang to 1.21.1 or later.

## Is CVE-2023-39320 being exploited?

There is no known exploitation of CVE-2023-39320 in the wild and no public exploit code.

Public exploit code:

- https://github.com/ayrustogaru/cve-2023-39320 (github_poc): https://github.com/ayrustogaru/cve-2023-39320

## Other vulnerabilities in Golang Go

- [CVE-2020-0601](https://insights.sbomify.com/CVE-2020-0601/): Microsoft Windows CryptoAPI Spoofing (high 8.1, exploited in the wild)
- [CVE-2026-27143](https://insights.sbomify.com/CVE-2026-27143/): Missing bound checks can lead to memory corruption in safe Go in cmd/compile (critical 9.8)
- [CVE-2024-24790](https://insights.sbomify.com/CVE-2024-24790/): Unexpected behavior from Is methods for IPv4-mapped IPv6 addresses in net/netip (critical 9.8)
- [CVE-2023-24540](https://insights.sbomify.com/CVE-2023-24540/): Improper handling of JavaScript whitespace in html/template (critical 9.8)
- [CVE-2023-24538](https://insights.sbomify.com/CVE-2023-24538/): Backticks not treated as string delimiters in html/template (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-39320 and fix it if it is affected.

What it is: CVE-2023-39320 is a critical code injection vulnerability in Golang Go, published on 8 Sep 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2023-39320 in the wild and no public exploit code.

Affected packages and fixed versions:
- golang (Bitnami): affected from 1.21.0; fixed in 1.21.1
- toolchain (Go): affected from 1.21.0-0; fixed in 1.21.1

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-2023-39320/ (Markdown: https://insights.sbomify.com/CVE-2023-39320/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-39320
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-39320
- OSV: https://osv.dev/vulnerability/CVE-2023-39320

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-39320/
Summaries are generated and may contain mistakes; the official description above is the record.