CVE-2026-23836 is a critical security vulnerability classified under CWE-20 (Improper Input Validation) affecting HotCRP, a widely used conference review software. The flaw was introduced in version 3.1 released in April 2024 and involves inadequate sanitization of user-supplied input in the formula evaluation engine. This improper input validation allows authenticated users with limited privileges to inject and execute arbitrary PHP code on the server. The vulnerability enables a complete compromise of the affected system, impacting confidentiality, integrity, and availability. The CVSS v3.1 score is 10.0, reflecting network attack vector, low attack complexity, required privileges, no user interaction, and scope change. Exploitation could lead to unauthorized data access, modification, or complete system takeover. The issue was addressed in HotCRP version 3.2, which includes proper input sanitization and validation mechanisms to prevent code injection. No public exploits have been reported yet, but the critical severity and ease of exploitation make this a high-risk vulnerability for organizations relying on HotCRP for managing academic conferences and peer reviews.

For European organizations, particularly universities, research institutions, and conference organizers using HotCRP 3.1, this vulnerability poses a severe risk. Exploitation could lead to unauthorized disclosure of sensitive research data, manipulation of peer review outcomes, and disruption of conference operations. The ability to execute arbitrary PHP code means attackers could implant backdoors, exfiltrate data, or disrupt services, potentially damaging reputations and violating data protection regulations such as GDPR. Given the criticality and the fact that the vulnerability requires only authenticated access with low privileges, insider threats or compromised user accounts could be leveraged to exploit this flaw. The impact extends beyond individual organizations to the broader academic and scientific community, undermining trust in conference processes and data integrity.

Immediate upgrade to HotCRP version 3.2 is the primary mitigation step, as it contains the patch that properly sanitizes input and prevents code injection. Until upgrade is possible, organizations should restrict access to HotCRP to trusted users only and enforce strong authentication and monitoring to detect suspicious activities. Implement network segmentation to isolate HotCRP servers from critical infrastructure. Conduct thorough audits of user privileges to minimize the number of users with formula editing capabilities. Employ web application firewalls (WAFs) with custom rules to detect and block suspicious input patterns targeting formula evaluation. Regularly monitor logs for unusual PHP execution or errors indicative of exploitation attempts. Educate administrators and users about the risks and signs of compromise related to this vulnerability.