GHSA-9ff2-p842-45wq: CSRF

Q: Which users are exposed to exploitation?

Only authenticated Contao back end users are exposed, and only for actions in modules that their account is permitted to access. The attacker must cause that logged-in user to load a crafted URL.

Q: Does exploitation require a valid request token or a privilege-escalation action?

No request token or user confirmation is required for the affected GET-dispatched actions. The verified key= actions are destructive or state-changing; no privilege-granting key= action was identified.

Q: Which back end actions should be considered at risk?

Actions dispatched through the key= parameter should be considered exposed because the GET-side guard only applies when an act parameter is present. This affects present and future key= actions rather than a single callback.

Published Oct 9, 2026

Updated

RequestTokenListener is the only generic REQUESTTOKEN 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 Software

2 affected componentsFixes available

composer/contao/core-bundle>=5.4.0-RC1<5.7.12

5.7.12

composer/contao/core-bundle>=4.0.0<5.3.50

5.3.50

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade composer/contao/core-bundle to a version that resolves this vulnerability.
Fixed in 5.7.12
Upgrade
Upgrade composer/contao/core-bundle to a version that resolves this vulnerability.
Fixed in 5.3.50

Event History

Oct 9, 2026

Advisory Published

via GitHub·08:54 PM

Data Sourced

via GitHub·08:54 PM

DescriptionSeverityWeaknessAffected Software

Frequently Asked Questions

Which users are exposed to exploitation?

Only authenticated Contao back end users are exposed, and only for actions in modules that their account is permitted to access. The attacker must cause that logged-in user to load a crafted URL.

Does exploitation require a valid request token or a privilege-escalation action?

No request token or user confirmation is required for the affected GET-dispatched actions. The verified key= actions are destructive or state-changing; no privilege-granting key= action was identified.

Which back end actions should be considered at risk?

Actions dispatched through the key= parameter should be considered exposed because the GET-side guard only applies when an act parameter is present. This affects present and future key= actions rather than a single callback.

GHSA-9ff2-p842-45wq: CSRF

Affected Software

Remediation

Event History

Frequently Asked Questions

Which users are exposed to exploitation?

Does exploitation require a valid request token or a privilege-escalation action?

Which back end actions should be considered at risk?

Company

Resources

Contact

Frequently Asked Questions

Which users are exposed to exploitation?

Does exploitation require a valid request token or a privilege-escalation action?

Which back end actions should be considered at risk?