CVE-2026-27743: SPIP referer_spam Plugin SQLi Vulnerability

CVE-2026-27743 Overview

CVE-2026-27743 is a critical unauthenticated SQL injection vulnerability affecting the SPIP referer_spam plugin versions prior to 1.3.0. The vulnerability exists in the referer_spam_ajouter and referer_spam_supprimer action handlers, which read the url parameter from GET requests and interpolate it directly into SQL LIKE clauses without proper input validation or parameterization. The affected endpoints lack authorization checks and do not implement SPIP's built-in action protections such as securiser_action(), enabling remote attackers to execute arbitrary SQL queries against the underlying database.

Critical Impact

Remote unauthenticated attackers can exploit this SQL injection vulnerability to extract sensitive data, modify database contents, or potentially achieve remote code execution depending on database configuration and privileges.

Affected Products

• SPIP referer_spam plugin versions prior to 1.3.0
• SPIP CMS installations with the vulnerable referer_spam plugin installed

Discovery Timeline

• 2026-02-25 - CVE-2026-27743 published to NVD
• 2026-02-26 - Last updated in NVD database

Technical Details for CVE-2026-27743

Vulnerability Analysis

This SQL injection vulnerability (CWE-89) stems from improper neutralization of special elements used in SQL commands. The referer_spam_ajouter and referer_spam_supprimer action handlers in the SPIP referer_spam plugin accept user-controlled input via the url GET parameter and directly concatenate this value into SQL LIKE clauses without any sanitization or use of prepared statements.

The vulnerability is particularly severe because the affected endpoints operate without authentication requirements. SPIP provides built-in security mechanisms like securiser_action() to protect action handlers, but the vulnerable code paths do not implement these protections. This allows any remote attacker to craft malicious requests containing SQL injection payloads without needing valid credentials or session tokens.

Successful exploitation could allow attackers to enumerate database contents, extract sensitive information including user credentials, modify or delete data, and potentially leverage database-specific features for further system compromise.

Root Cause

The root cause is the direct interpolation of untrusted user input from the url GET parameter into SQL queries. The vulnerable code constructs SQL LIKE clauses by string concatenation rather than using parameterized queries or SPIP's database abstraction layer with proper escaping. Additionally, the absence of authorization checks and SPIP action security tokens (securiser_action()) removes the authentication barrier that would otherwise limit exposure.

Attack Vector

The attack is network-based and requires no authentication or user interaction. An attacker sends crafted HTTP GET requests to the referer_spam_ajouter or referer_spam_supprimer action endpoints with a malicious url parameter containing SQL injection payloads. Since LIKE clauses are targeted, attackers can use wildcard characters and boolean-based or time-based blind injection techniques to extract data.

The exploitation path involves:

1. Identifying a SPIP installation with the vulnerable referer_spam plugin
2. Crafting GET requests to the vulnerable action handlers
3. Injecting SQL payloads through the url parameter
4. Extracting data or manipulating the database through iterative queries

Technical details and proof-of-concept information can be found in the VulnCheck SQL Injection Advisory and the Chocapikk Plugin Vulnerabilities research publication.

Detection Methods for CVE-2026-27743

Indicators of Compromise

• HTTP GET requests to SPIP action endpoints containing referer_spam_ajouter or referer_spam_supprimer with suspicious url parameter values
• SQL injection patterns in web server access logs including UNION, SELECT, single quotes, OR statements, and time-based payload indicators (e.g., SLEEP, WAITFOR)
• Unusual database query patterns or errors in application logs
• Unexpected data exfiltration or modifications in the SPIP database

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block SQL injection patterns in GET parameters targeting SPIP action endpoints
• Monitor web server logs for requests containing referer_spam_ajouter or referer_spam_supprimer actions with anomalous url parameter values
• Deploy database activity monitoring to detect unusual query patterns or unauthorized data access
• Use intrusion detection systems (IDS) with signatures for common SQL injection attack vectors

Monitoring Recommendations

• Enable detailed logging for SPIP action requests and database queries
• Configure alerting for HTTP requests containing SQL metacharacters targeting the affected action handlers
• Establish baseline database activity patterns and alert on deviations
• Review SPIP plugin inventory to identify installations of referer_spam versions prior to 1.3.0

How to Mitigate CVE-2026-27743

Immediate Actions Required

• Upgrade the SPIP referer_spam plugin to version 1.3.0 or later immediately
• If immediate upgrade is not possible, disable or remove the referer_spam plugin until patching can be completed
• Audit database logs for evidence of SQL injection attempts or successful exploitation
• Review and rotate database credentials if compromise is suspected
• Implement WAF rules to block SQL injection attempts as a defense-in-depth measure

Patch Information

The vulnerability has been addressed in SPIP referer_spam plugin version 1.3.0. The security fix is available in the SPIP Commit Reference. Administrators should update through the SPIP plugin management interface or download the patched version from the SPIP Referer Spam Plugin page. Additional information about the security update is available in the SPIP Security Update Release announcement.

Workarounds

• Disable or uninstall the referer_spam plugin if not actively needed until an upgrade can be performed
• Implement network-level access controls to restrict access to SPIP administrative and action endpoints
• Deploy a Web Application Firewall with SQL injection detection rules in front of the SPIP installation
• Block direct access to action URLs at the web server level if the referer_spam functionality is not required

# Apache configuration to block access to vulnerable action handlers
<Location /spip.php>
    <If "%{QUERY_STRING} =~ /action=referer_spam_(ajouter|supprimer)/">
        Require all denied
    </If>
</Location>