# CVE-2026-107848: Contao: Cross-site request forgery in custom backend actions

> An attacker can trick authenticated backend users into executing state-changing actions via crafted URLs due to missing CSRF token validation on specific GET requests.

- **Severity:** Low 3.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 9 Oct 2026
- **Updated:** 13 Oct 2026
- **Also known as:** GHSA-9ff2-p842-45wq

## What is CVE-2026-107848?

CVE-2026-107848 is a low-severity vulnerability in contao, published on 9 Oct 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

Contao is an Open Source CMS. From version 4.0.0 until 5.3.50 and 5.7.12, RequestTokenListener validates REQUEST_TOKEN only for POST requests, while the declarative GET guard runs only when an act parameter is present. Backend actions dispatched through the key parameter can therefore execute without a CSRF token when an authenticated backend user loads an attacker-controlled URL. Reachable actions remain limited to modules available to that user, and the advisory demonstrates destructive or state-changing actions rather than privilege escalation. This issue is fixed in versions 5.3.50 and 5.7.12.

Weakness: CWE-352 (Cross-Site Request Forgery)

## Which versions are affected by CVE-2026-107848?

4 open source packages ship an affected version, including contao/core-bundle.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `contao/core-bundle` | Packagist | From 4.0.0 | 5.3.50 |
| `contao/core-bundle` | Packagist | From 4.0.0 | 5.3.50 |
| `contao/core-bundle` | Packagist | From 5.4.0-RC1 | 5.7.12 |
| `contao/core-bundle` | Packagist | From 5.4.0-RC1 | 5.7.12 |

## How do I fix CVE-2026-107848?

Upgrade contao/core-bundle to a fixed version for your release line: 5.3.50 or 5.7.12.

## Is CVE-2026-107848 being exploited?

There is no known exploitation of CVE-2026-107848 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-107848 and fix it if it is affected.

What it is: CVE-2026-107848 is a low-severity vulnerability in contao, published on 9 Oct 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-107848 in the wild and no public exploit code.

Affected packages and fixed versions:
- contao/core-bundle (Packagist): affected from 4.0.0; fixed in 5.3.50
- contao/core-bundle (Packagist): affected from 4.0.0; fixed in 5.3.50
- contao/core-bundle (Packagist): affected from 5.4.0-RC1; fixed in 5.7.12
- contao/core-bundle (Packagist): affected from 5.4.0-RC1; fixed in 5.7.12

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-2026-107848/ (Markdown: https://insights.sbomify.com/CVE-2026-107848/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-107848
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-107848
- OSV: https://osv.dev/vulnerability/CVE-2026-107848

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-107848/
Summaries are generated and may contain mistakes; the official description above is the record.