CVE-2026-57232 Overview
CVE-2026-57232 is a Server-Side Request Forgery (SSRF) vulnerability in Contao, an open source Content Management System (CMS). The flaw exists in the Feed Reader front-end module, which passes configured RSS feed URLs to the HTTP client without scheme or private-address validation. A backend user with module-edit permissions can coerce the server to request internal network services, loopback addresses, or cloud metadata endpoints. The vulnerability affects versions 5.3.35 through 5.3.47 and 5.7.0-RC1 through 5.7.8, and is classified under [CWE-918].
Critical Impact
Authenticated backend users can pivot the Contao server into internal networks and access cloud instance metadata services, exposing credentials and internal HTTP endpoints.
Affected Products
- Contao CMS versions 5.3.35 through 5.3.47
- Contao CMS versions 5.7.0-RC1 through 5.7.8
- Contao core-bundle Feed Reader front-end module
Discovery Timeline
- 2026-07-31 - CVE-2026-57232 published to NVD
- 2026-08-03 - Last updated in NVD database
Technical Details for CVE-2026-57232
Vulnerability Analysis
The vulnerability resides in core-bundle/src/Controller/FrontendModule/FeedReaderController.php. The getResponse() function iterates over configured feed URLs and passes each directly to the HTTP client through $this->feedIo->read($url, new Feed()). No validation is performed on the URL scheme or destination host before the outbound request executes.
Contao's data container array (DCA) field definition for rss_feed in tl_module.php also lacks URL scheme or host validation. The HTTP client is wired as @psr18.http_client (Symfony HttpClient) without NoPrivateNetworkHttpClient in the pipeline, so requests to private ranges are not blocked.
An attacker with module-edit permissions can configure a feed module URL pointing at internal services. When the module renders, the Contao server issues the request from its own network position, returning responses or side effects that the attacker can observe.
Root Cause
The root cause is missing input validation on user-supplied URLs combined with an unhardened HTTP client. Neither the DCA layer nor the controller enforces an allowlist of schemes (for example, restricting to http and https) or blocks RFC 1918 addresses, link-local ranges, and metadata endpoints such as 169.254.169.254.
Attack Vector
Exploitation requires authenticated access to the Contao backend with permission to edit the Feed Reader module. The attacker sets the rss_feed URL to an internal target, then triggers module rendering to force the server to issue the request. Targets include cloud metadata endpoints, internal admin panels, and databases exposed only on loopback interfaces. See the GitHub Security Advisory GHSA-87mg-5grr-rhwh for additional technical details.
Detection Methods for CVE-2026-57232
Indicators of Compromise
- Outbound HTTP requests from the Contao web server to RFC 1918 addresses, 127.0.0.0/8, or 169.254.169.254
- Feed Reader module records in tl_module where rss_feed contains internal hostnames, IP literals, or non-http(s) schemes
- Unexpected access log entries on internal services originating from the Contao application server IP
Detection Strategies
- Audit the tl_module database table for Feed Reader entries and validate that all rss_feed URLs resolve to legitimate external hosts
- Inspect web server egress logs for HTTP client requests carrying the feedIo user agent to non-public destinations
- Correlate backend user activity in Contao audit logs with subsequent outbound traffic from the application server
Monitoring Recommendations
- Enable egress filtering and log any HTTP requests from the Contao host to internal RFC 1918 or metadata IP ranges
- Monitor cloud provider metadata endpoint access patterns for anomalous requests from web application instances
- Alert on new or modified Feed Reader modules created by backend users with elevated permissions
How to Mitigate CVE-2026-57232
Immediate Actions Required
- Upgrade Contao to version 5.3.48 or later, which contains the fix for CVE-2026-57232
- Review all existing Feed Reader modules and remove entries pointing to internal or non-standard URLs
- Restrict backend module-edit permissions to trusted administrators only
Patch Information
Contao released the fix in version 5.3.48. The corrective commits are available at Contao commit 27f6201 and Contao commit 53b939f. The fix adds URL validation and wires the HTTP client with SSRF protections.
Workarounds
- Deploy network-level egress controls that block outbound traffic from the Contao server to RFC 1918, loopback, and cloud metadata address ranges
- Temporarily disable the Feed Reader front-end module until the upgrade is applied
- Restrict backend accounts with module-edit rights to a minimal set of vetted users
# Upgrade Contao via Composer to the patched release
composer require contao/core-bundle:^5.3.48
composer update contao/core-bundle --with-dependencies
vendor/bin/contao-console contao:migrate
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
