GHSA-9ff2-p842-45wq CVE-2026-107848
Contao: Cross-site request forgery in custom backend actions
- Severity
- 3.5 / 10
- Low · CVSS 3.1
- Exploit chance (EPSS)
- 0.11%
- Chance of exploitation in the next 30 days. Higher than 1.56% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-352 Cross-Site Request Forgery (CSRF)
- Fix
5.3.50- Upgrade contao/core-bundle to this version or later
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 versions
Packagist
| Package | Vulnerable | Fixed in |
|---|---|---|
| contao/core-bundle | >= 4.0.0, < 5.3.50 |
5.3.50 |
| contao/core-bundle | >= 5.4.0-RC1, < 5.7.12 |
5.7.12 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
contao/core-bundle Packagist → 5.3.50
- composer
composer require contao/core-bundle:^5.3.50
Severity breakdown
CVSS 3.1 3.5
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- Low
- Availability
- None
Weakness
CWE-352: Cross-Site Request Forgery (CSRF)
The web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor.
How to prevent it
- Architecture and Design: Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid [REF-1482]. For example, use anti-CSRF packages such as the OWASP CSRFGuard. [REF-330] Another example is the ESAPI Session Management control, which includes a component for CSRF. [REF-45]
- Implementation: Ensure that the application is free of cross-site scripting issues (CWE-79), because most CSRF defenses can be bypassed using attacker-controlled script.
- Architecture and Design: Generate a unique nonce for each form, place the nonce into the form, and verify the nonce upon receipt of the form. Be sure that the nonce is not predictable (CWE-330). [REF-332]
- Architecture and Design: Identify especially dangerous operations. When the user performs a dangerous operation, send a separate confirmation request to ensure that the user intended to perform that operation.
- Architecture and Design: Use the "double-submitted cookie" method as described by Felten and Zeller: When a user visits a site, the site should generate a pseudorandom value and set it as a cookie on the user's machine. The site should require every form submission to include this value as a form value and also as a cookie value. When a POST request is sent to the site, the request should only be considered valid if the form value and the cookie value are the same. Because of the same-origin policy, an attacker cannot read or modify the value stored in the cookie. To successfully submit a form on behalf of the user, the attacker would have to correctly guess the pseudorandom value. If the pseudorandom value is cryptographically strong, this will be prohibitively difficult. This technique requires Javascript, so it may not work for browsers that have Javascript disabled. [REF-331]
- Architecture and Design: Do not use the GET method for any request that triggers a state change.
- Implementation: Check the HTTP Referer header to see if the request originated from an expected page. This could break legitimate functionality, because users or proxies may have disabled sending the Referer for privacy reasons.
References
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-q6wp-fr43-gm9v Contao: Improper access control in the preview links module | Medium | Also affects contao/core-bundle |
| GHSA-5974-gfqc-wrcm Contao: Improper access control in the table access voter | Medium | Also affects contao/core-bundle |
| GHSA-mrvp-7wmx-5m4h Contao: Path traversal in the images controller | Medium | Also affects contao/core-bundle |
| GHSA-mfxh-vp55-7gc6 Contao: The registration module re-sends activation mails | Medium | Also affects contao/core-bundle |
| GHSA-x2rp-9qf7-2fmq Contao: Protected page content is disclosed to anonymous visitors after contao.search.index_protected is disabled | Medium | Also affects contao/core-bundle |
| GHSA-grm4-wm43-9jh5 Contao: Possible path traversal in job download URIs | Low | Also affects contao/core-bundle |
| GHSA-87mg-5grr-rhwh Contao: Server-Side Request Forgery (SSRF) via Unvalidated RSS Feed URL in Feed Reader Module | Low | Also affects contao/core-bundle |
| GHSA-3mr9-p497-58f6 Contao crawler leaks auth credentials to external hosts | Low | Also affects contao/core-bundle |
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