CVE-2026-107848 is a low-severity (CVSS 3.5) Cross-Site Request Forgery (CSRF) vulnerability in contao/core-bundle. A fix is available for contao/core-bundle — see the affected versions and patch details below.
Contao: Cross-site request forgery in custom backend actions
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-107848.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-107848 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 394,803 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
contao/core-bundle🐘contao/core-bundleReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
RequestTokenListener is the only generic REQUEST_TOKEN validator in Contao and it only runs on POST. On the GET side the guard is local and declarative, and it only fires when an act parameter is present. Every back end action dispatched through a different parameter therefore has no CSRF protection at all. This is a family rather than a single bug.
Impact
An attacker who gets a logged in back end user to load a URL performs back end actions as that user, with no token and no confirmation. Because the exposure follows from the dispatch mechanism rather than from one callback, every present and future key= action inherits it.
Honest bound. The victim must be authenticated in the back end and must load the URL, and the reachable actions are limited to the modules that user can access. We have not found a key= action that grants privileges; the ones we verified are destructive or state changing rather than escalating.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | contao/core-bundle | ≥ 4.0.0&&< 5.3.50 | 5.3.50composer require contao/core-bundle:^5.3.50 |
| 🐘Packagist | contao/core-bundle | ≥ 5.4.0-RC1&&< 5.7.12 | 5.7.12composer require contao/core-bundle:^5.7.12 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for contao/core-bundle, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update contao/core-bundle to 5.3.50 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-107848 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is CVE-2026-107848 in your dependencies?
Find it across Packagist, including transitive dependencies.