# CVE-2021-47964: Schlix CMS 2.2.6-6 Remote Code Execution via core.blockmanager

> Authenticated attackers can execute arbitrary PHP code by uploading malicious extension packages in Schlix CMS.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 15 May 2026
- **Updated:** 18 May 2026
- **Also known as:** GHSA-r3mq-4wxp-p8vq

## What is CVE-2021-47964?

CVE-2021-47964 is a high-severity code injection vulnerability in Schlix CMS, published on 15 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Schlix CMS 2.2.6-6 contains a remote code execution vulnerability that allows authenticated attackers to execute arbitrary PHP code by uploading malicious extension packages through the block manager. Attackers can upload a crafted ZIP file containing PHP code in the packageinfo.inc file and trigger execution by accessing the About tab of the installed extension.

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

## Which versions are affected by CVE-2021-47964?


## How do I fix CVE-2021-47964?

No fix has been published for CVE-2021-47964 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-47964 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-47964 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-47964 and fix it if it is affected.

What it is: CVE-2021-47964 is a high-severity code injection vulnerability in Schlix CMS, published on 15 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-47964 exists.

Affected product: Schlix CMS. 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-2021-47964/ (Markdown: https://insights.sbomify.com/CVE-2021-47964/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47964
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47964
- OSV: https://osv.dev/vulnerability/CVE-2021-47964

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47964/
Summaries are generated and may contain mistakes; the official description above is the record.