# CVE-2026-19418: TYPO3 CMS - Broken Access Control in Backend and Install Tool

> Attackers can bypass backend access controls via referrer checks, allowing unauthorized actions with victim privileges if they can execute JavaScript on the site.

- **Severity:** High 7.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:A/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:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 11 Aug 2026
- **Updated:** 11 Aug 2026
- **Also known as:** GHSA-68jx-f42c-7599

## What is CVE-2026-19418?

CVE-2026-19418 is a high-severity vulnerability in TYPO3 CMS, published on 11 Aug 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

The referrer enforcement introduced with TYPO3-CORE-SA-2020-006 (CVE-2020-11069) became ineffective in TYPO3 v13.0, where TYPO3 CMS started serving the backend and Install Tool applications from the site's main entry script instead of the dedicated typo3/ directory.

Whether a request originated from the backend or Install Tool itself was determined by comparing the referrer against the directory of the entry script, which since then is the site root. As a consequence, requests originating from any script running on one of the TYPO3 instance's own domains, such as a frontend page, were accepted by backend routes and Install Tool endpoints.

Attackers able to execute JavaScript on one of those domains, for instance by exploiting a cross-site scripting vulnerability, could invoke these endpoints via Fetch/XHR with the privileges of an authenticated victim's user session. This issue affects TYPO3 CMS versions 13.0.0-13.4.33 and 14.0.0-14.3.5.

Weakness: CWE-352 (Cross-Site Request Forgery), CWE-346 (Origin Validation Error)

## Which versions are affected by CVE-2026-19418?

4 open source packages ship an affected version, including typo3/cms-backend and typo3/cms-core.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `typo3/cms-backend` | Packagist | From 13.0.0 | 13.4.34 |
| `typo3/cms-backend` | Packagist | From 13.0.0 | 13.4.34 |
| `typo3/cms-core` | Packagist | From 14.0.0 | 14.3.6 |
| `typo3/cms-core` | Packagist | From 14.0.0 | 14.3.6 |

## How do I fix CVE-2026-19418?

Upgrade typo3/cms-backend to 13.4.34 or later.

## Is CVE-2026-19418 being exploited?

There is no known exploitation of CVE-2026-19418 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-19418 and fix it if it is affected.

What it is: CVE-2026-19418 is a high-severity vulnerability in TYPO3 CMS, published on 11 Aug 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-2026-19418 in the wild and no public exploit code.

Affected packages and fixed versions:
- typo3/cms-backend (Packagist): affected from 13.0.0; fixed in 13.4.34
- typo3/cms-backend (Packagist): affected from 13.0.0; fixed in 13.4.34
- typo3/cms-core (Packagist): affected from 14.0.0; fixed in 14.3.6
- typo3/cms-core (Packagist): affected from 14.0.0; fixed in 14.3.6

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-2026-19418/ (Markdown: https://insights.sbomify.com/CVE-2026-19418/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-19418
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-19418
- OSV: https://osv.dev/vulnerability/CVE-2026-19418

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-19418/
Summaries are generated and may contain mistakes; the official description above is the record.