# CVE-2021-43281: Code injection in n/a

> An admin with settings management permissions can inject PHP code via the Admin CP, leading to remote code execution.

- **Severity:** High 7.2 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 4 Nov 2021
- **Updated:** 4 Aug 2024

## What is CVE-2021-43281?

CVE-2021-43281 is a high-severity code injection vulnerability in Mybb Mybb, published on 4 Nov 2021. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

MyBB before 1.8.29 allows Remote Code Injection by an admin with the "Can manage settings?" permission. The Admin CP's Settings management module does not validate setting types correctly on insertion and update, making it possible to add settings of supported type "php" with PHP code, executed on Change Settings pages.

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

## Which versions are affected by CVE-2021-43281?

It affects 1 product.


Products: Mybb Mybb.

## How do I fix CVE-2021-43281?

No fix has been published for CVE-2021-43281 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-43281 being exploited?

There is no known exploitation of CVE-2021-43281 in the wild and no public exploit code.

## Other vulnerabilities in Mybb Mybb

- [CVE-2011-10018](https://insights.sbomify.com/CVE-2011-10018/): myBB 1.6.4 Backdoor Arbitrary Command Execution (critical 10.0)
- [CVE-2015-2786](https://insights.sbomify.com/CVE-2015-2786/): Information disclosure in n/a (critical 10.0)
- [CVE-2011-5133](https://insights.sbomify.com/CVE-2011-5133/): Cross-site scripting in n/a (critical 10.0)
- [CVE-2006-0218](https://insights.sbomify.com/CVE-2006-0218/): SQL injection in n/a (critical 10.0)
- [CVE-2020-22612](https://insights.sbomify.com/CVE-2020-22612/): Code injection in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-43281 and fix it if it is affected.

What it is: CVE-2021-43281 is a high-severity code injection vulnerability in Mybb Mybb, published on 4 Nov 2021. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-43281 in the wild and no public exploit code.

Affected product: Mybb Mybb. 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-2021-43281/ (Markdown: https://insights.sbomify.com/CVE-2021-43281/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-43281
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-43281
- OSV: https://osv.dev/vulnerability/CVE-2021-43281

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-43281/
Summaries are generated and may contain mistakes; the official description above is the record.