The SPIP referer_spam plugin, widely used for managing spam referrer data in SPIP CMS environments, contains a severe SQL injection vulnerability identified as CVE-2026-27743. This vulnerability affects all versions prior to 1.3.0 and resides in two action handlers: referer_spam_ajouter and referer_spam_supprimer. These handlers accept a url parameter via GET requests and directly embed it into SQL LIKE clauses without any input sanitization, validation, or use of prepared statements. Furthermore, these endpoints do not enforce any authorization or authentication checks and omit the use of SPIP's securiser_action() function, which is designed to protect action handlers from unauthorized access. As a result, remote attackers can craft malicious URLs that execute arbitrary SQL commands on the backend database, potentially leading to unauthorized data access, data manipulation, or denial of service. The vulnerability is remotely exploitable without any user interaction or privileges, increasing its risk profile. The CVSS 4.0 vector (AV:N/AC:L/AT:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N) indicates network attack vector, low complexity, no authentication or user interaction required, and high impact on confidentiality and integrity. Although no public exploits have been reported yet, the critical nature of this flaw demands immediate attention from administrators of SPIP installations using the referer_spam plugin.

The impact of CVE-2026-27743 is significant for organizations running SPIP CMS with the vulnerable referer_spam plugin. Successful exploitation allows attackers to execute arbitrary SQL queries remotely without authentication, potentially leading to full database compromise. This can result in unauthorized disclosure of sensitive data, data tampering, or deletion, severely affecting confidentiality and integrity. Additionally, attackers could disrupt service availability by corrupting database contents or causing application crashes. Given the lack of authentication and user interaction requirements, automated exploitation is feasible, increasing the risk of widespread attacks. Organizations relying on SPIP for content management, especially those handling sensitive or regulated data, face increased risk of data breaches, reputational damage, and compliance violations. The absence of known exploits currently provides a window for proactive mitigation, but the critical severity score underscores the urgency of addressing this vulnerability.

To mitigate CVE-2026-27743, organizations should immediately upgrade the referer_spam plugin to version 1.3.0 or later where the vulnerability is fixed. If upgrading is not immediately possible, apply the following specific mitigations: 1) Implement input validation and sanitization on the url parameter to prevent injection of malicious SQL syntax. 2) Modify the referer_spam_ajouter and referer_spam_supprimer handlers to use parameterized queries or prepared statements instead of direct string interpolation in SQL commands. 3) Enforce authorization checks on these action handlers to restrict access to authenticated and authorized users only. 4) Utilize SPIP’s securiser_action() function to protect action endpoints from unauthorized invocation. 5) Monitor web server logs for suspicious GET requests targeting these endpoints and unusual database errors indicative of injection attempts. 6) Restrict database user permissions to minimize potential damage from SQL injection. 7) Conduct regular security audits and penetration testing focused on input validation and access controls. These targeted steps go beyond generic advice and address the root causes of the vulnerability.