# CVE-2021-45444: Code injection in n/a

> Attackers can execute arbitrary code via recursive prompt substitution if they control command output in the zsh prompt.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 13 Feb 2022
- **Updated:** 4 Aug 2024
- **Also known as:** ALPINE-CVE-2021-45444, ALSA-2022:2120, AZL-8586, CLSA-2022-1648567648, CLSA-2022-1648567705, DEBIAN-CVE-2021-45444, DLA-2926-1, DSA-5078-1, GHSA-735j-r9q6-48mw, MGASA-2022-0073, OESA-2022-1567, OESA-2022-2094, RHSA-2022:2120, RLSA-2022:2120, UBUNTU-CVE-2021-45444, openSUSE-SU-2024:11959-1

## What is CVE-2021-45444?

CVE-2021-45444 is a high-severity code injection vulnerability in Apple Mac Os X, published on 13 Feb 2022. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

In zsh before 5.8.1, an attacker can achieve code execution if they control a command output inside the prompt, as demonstrated by a %F argument. This occurs because of recursive PROMPT_SUBST expansion.

## Which versions are affected by CVE-2021-45444?

It affects 5 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `zsh` | AlmaLinux:8 | All versions | 5.5.1-9.el8 |
| `zsh-html` | AlmaLinux:8 | All versions | 5.5.1-9.el8 |
| `zsh-html` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.5.1-9.el8 |
| `zsh` | Red Hat:enterprise_linux:8::baseos | All versions | 0:5.5.1-9.el8 |
| `zsh-debuginfo` | Red Hat:enterprise_linux:8::baseos | All versions | 0:5.5.1-9.el8 |
| `zsh-debugsource` | Red Hat:enterprise_linux:8::baseos | All versions | 0:5.5.1-9.el8 |
| `zsh` | Rocky Linux:8 | All versions | 0:5.5.1-9.el8 |
| `zsh` | openSUSE:Tumbleweed | All versions | 5.8.1-1.1 |

Products: Apple Mac Os X, Apple Macos, Debian Debian Linux, Fedoraproject Fedora, Zsh Zsh.

## How do I fix CVE-2021-45444?

Upgrade to a fixed version.

## Is CVE-2021-45444 being exploited?

There is no known exploitation of CVE-2021-45444 in the wild and no public exploit code.

## Other vulnerabilities in Apple Mac Os X

- [CVE-2014-7169](https://insights.sbomify.com/CVE-2014-7169/): GNU Bourne-Again Shell (Bash) Arbitrary Code Execution (critical 9.8, exploited in the wild)
- [CVE-2014-6271](https://insights.sbomify.com/CVE-2014-6271/): GNU Bourne-Again Shell (Bash) Arbitrary Code Execution (critical 9.8, exploited in the wild)
- [CVE-2012-1823](https://insights.sbomify.com/CVE-2012-1823/): PHP-CGI Query String Parameter (critical 9.8, exploited in the wild)
- [CVE-2021-30713](https://insights.sbomify.com/CVE-2021-30713/): Apple macOS Unspecified (high 7.8, exploited in the wild)
- [CVE-2019-8526](https://insights.sbomify.com/CVE-2019-8526/): Apple macOS Use-After-Free (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-45444 and fix it if it is affected.

What it is: CVE-2021-45444 is a high-severity code injection vulnerability in Apple Mac Os X, published on 13 Feb 2022. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-45444 in the wild and no public exploit code.

Affected product: Apple Mac Os X. 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-2021-45444/ (Markdown: https://insights.sbomify.com/CVE-2021-45444/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-45444
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-45444
- OSV: https://osv.dev/vulnerability/CVE-2021-45444

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-45444/
Summaries are generated and may contain mistakes; the official description above is the record.