CVE-2026-41177: Squidex CMS Blind SSRF Vulnerability

CVE-2026-41177 Overview

CVE-2026-41177 is a Blind Server-Side Request Forgery (SSRF) vulnerability affecting Squidex, an open source headless content management system and content management hub. Prior to version 7.23.0, the Squidex Restore API fails to validate the URI scheme of the user-supplied Url parameter, allowing the use of the file:// protocol. This allows an authenticated administrator to force the backend server to interact with the local filesystem, which can lead to Local File Interaction (LFI) and potential disclosure of sensitive system information through side-channel analysis of internal logs.

Critical Impact

Authenticated administrators can exploit this vulnerability to read sensitive files from the server's local filesystem, potentially exposing configuration files, credentials, and other system information through side-channel analysis.

Affected Products

• Squidex versions prior to 7.23.0
• Squidex Restore API endpoint

Discovery Timeline

• 2026-04-22 - CVE CVE-2026-41177 published to NVD
• 2026-04-23 - Last updated in NVD database

Technical Details for CVE-2026-41177

Vulnerability Analysis

This vulnerability is classified under CWE-73 (External Control of File Name or Path). The core issue lies in the Squidex Restore API's lack of proper URI scheme validation when processing user-supplied URL parameters. When an administrator provides a URL to the restore functionality, the application does not restrict the protocol scheme, enabling the use of file:// URIs instead of the expected http:// or https:// schemes.

The attack requires administrator-level authentication, limiting the pool of potential attackers. However, once an attacker gains administrative access—whether through credential compromise, social engineering, or insider threats—they can leverage this SSRF vulnerability to interact with the local filesystem of the backend server.

The blind nature of this SSRF means that the attacker does not receive direct file contents in the response. Instead, they must rely on side-channel analysis, such as observing timing differences, error messages, or internal log entries to infer information about the filesystem and its contents.

Root Cause

The root cause is insufficient input validation on the Url parameter within the Restore API. The application accepts arbitrary URI schemes without enforcing an allowlist of permitted protocols. This design flaw enables attackers to abuse the file:// protocol handler to force the server to access local filesystem resources, bypassing the intended network-based restore functionality.

Attack Vector

The attack is conducted over the network and requires high privileges (administrator authentication). An attacker with administrative credentials can craft a malicious request to the Restore API endpoint, specifying a file:// URL pointing to sensitive local files. The server processes this request and attempts to read the specified file, with the results potentially observable through internal logs or error responses.

The vulnerability mechanism works as follows: when a restore operation is initiated, the backend server fetches the content from the provided URL. By substituting a file:// path (such as file:///etc/passwd on Linux or file:///C:/Windows/System32/config/SAM on Windows), the attacker can force the server to read local files. The blind nature requires the attacker to analyze server behavior, timing, or logs to determine if the file access succeeded and what information was retrieved.

For technical details, see the GitHub Security Advisory.

Detection Methods for CVE-2026-41177

Indicators of Compromise

• Unusual requests to the Restore API endpoint containing file:// protocol schemes in the URL parameter
• Administrative API calls attempting to access local filesystem paths such as /etc/passwd, /etc/shadow, or Windows system directories
• Log entries showing file access attempts from the Squidex application process to sensitive system files
• Error messages or exceptions related to file:// protocol handling in application logs

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block requests containing file:// protocol in POST parameters to the Restore API
• Monitor authentication logs for suspicious administrator login patterns that precede exploit attempts
• Configure application-level logging to capture all Restore API requests with full URL parameters for forensic analysis
• Deploy network-level monitoring to detect outbound connections from the Squidex server that originate from file-based SSRF reconnaissance

Monitoring Recommendations

• Enable verbose logging on the Squidex application to capture detailed information about Restore API operations
• Set up alerts for any Restore API requests that contain non-HTTP/HTTPS protocol schemes
• Monitor filesystem access patterns from the Squidex process for reads of sensitive system files
• Implement Security Information and Event Management (SIEM) correlation rules to identify SSRF attack patterns across multiple log sources

How to Mitigate CVE-2026-41177

Immediate Actions Required

• Upgrade Squidex to version 7.23.0 or later immediately
• Review administrator account access and enforce principle of least privilege
• Audit recent Restore API activity for any suspicious URL patterns or unauthorized access attempts
• Consider temporarily disabling the Restore API functionality if immediate patching is not possible

Patch Information

The vulnerability has been fixed in Squidex version 7.23.0. The patch introduces proper URI scheme validation to restrict the Url parameter to safe protocols (HTTP/HTTPS), preventing the use of file:// and other dangerous schemes.

The fix can be reviewed in the GitHub commit b81d75e1d9c1a8e30993c2ee59b350002b9aeda4.

For complete security advisory details, refer to the Squidex Security Advisory GHSA-45fq-w37p-qfw5.

Workarounds

• Implement network-level restrictions to limit the Squidex server's ability to access the local filesystem via firewall rules or container isolation
• Deploy a reverse proxy or WAF in front of Squidex to filter requests containing file:// protocol schemes
• Restrict administrator access to trusted users only and implement multi-factor authentication for administrative accounts
• If the Restore functionality is not required, consider disabling the endpoint entirely at the application or network level until patching is complete

# Example: Block file:// protocol at WAF level (ModSecurity rule)
SecRule ARGS "@contains file://" "id:100001,phase:2,deny,status:403,msg:'Blocked file:// protocol in request'"