# CVE-2026-23923: Unauthenticated arbitrary PHP class instantiation

> Unauthenticated attackers can instantiate arbitrary PHP classes via the Frontend validate action, potentially leading to code execution depending on the environment.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 24 Mar 2026
- **Updated:** 25 Mar 2026
- **Also known as:** GHSA-4mp5-p9jh-3rv5

## What is CVE-2026-23923?

CVE-2026-23923 is a medium-severity code injection vulnerability in Zabbix Zabbix, published on 24 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An unauthenticated attacker can exploit the Frontend 'validate' action to blindly instantiate arbitrary PHP classes. The impact depends on environment setup but appears limited at this time.

Weakness: CWE-470 (Use of Externally-Controlled Input to Select Classes or Code)

## Which versions are affected by CVE-2026-23923?

It affects 1 product.


Products: Zabbix Zabbix.

## How do I fix CVE-2026-23923?

No fix has been published for CVE-2026-23923 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-23923 being exploited?

There is no known exploitation of CVE-2026-23923 in the wild and no public exploit code.

## Other vulnerabilities in Zabbix Zabbix

- [CVE-2022-23131](https://insights.sbomify.com/CVE-2022-23131/): Zabbix Frontend Authentication Bypass (critical 9.1, exploited in the wild)
- [CVE-2007-0640](https://insights.sbomify.com/CVE-2007-0640/): Memory corruption in n/a (critical 10.0)
- [CVE-2024-42327](https://insights.sbomify.com/CVE-2024-42327/): SQL injection in user.get API (critical 9.9)
- [CVE-2024-22116](https://insights.sbomify.com/CVE-2024-22116/): Remote code execution within ping script (critical 9.9)
- [CVE-2013-3738](https://insights.sbomify.com/CVE-2013-3738/): Code injection in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-23923 and fix it if it is affected.

What it is: CVE-2026-23923 is a medium-severity code injection vulnerability in Zabbix Zabbix, published on 24 Mar 2026. 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-2026-23923 in the wild and no public exploit code.

Affected product: Zabbix Zabbix. 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-2026-23923/ (Markdown: https://insights.sbomify.com/CVE-2026-23923/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23923
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23923
- OSV: https://osv.dev/vulnerability/CVE-2026-23923

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23923/
Summaries are generated and may contain mistakes; the official description above is the record.