# CVE-2026-18856: Poesis Rhymix CMS Data Import importer.admin.controller.php procImporterAdminCheckXmlFile server-side request forgery

> Remote attackers can exploit a server-side request forgery vulnerability in the Rhymix CMS Data Import module to access internal resources.

- **Severity:** Medium 5.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 5 Aug 2026
- **Updated:** 5 Aug 2026
- **Also known as:** GHSA-26jj-c4g2-h8m6

## What is CVE-2026-18856?

CVE-2026-18856 is a medium-severity server-side request forgery vulnerability in Poesis Rhymix CMS, published on 5 Aug 2026. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

A vulnerability was determined in Poesis Rhymix CMS up to 2.1.33. This impacts the function procImporterAdminCheckXmlFile of the file modules/importer/importer.admin.controller.php of the component Data Import Module. This manipulation of the argument filename causes server-side request forgery. The attack is possible to be carried out remotely. The exploit has been publicly disclosed and may be utilized. Upgrading to version 2.1.34 will fix this issue. It is recommended to upgrade the affected component.

Weakness: CWE-918 (Server-Side Request Forgery)

## Which versions are affected by CVE-2026-18856?


## How do I fix CVE-2026-18856?

No fix has been published for CVE-2026-18856 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-18856 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-18856 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-18856 and fix it if it is affected.

What it is: CVE-2026-18856 is a medium-severity server-side request forgery vulnerability in Poesis Rhymix CMS, published on 5 Aug 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-18856 exists.

Affected product: Poesis Rhymix 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-2026-18856/ (Markdown: https://insights.sbomify.com/CVE-2026-18856/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-18856
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-18856
- OSV: https://osv.dev/vulnerability/CVE-2026-18856

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-18856/
Summaries are generated and may contain mistakes; the official description above is the record.