CVE-2025-11602 is a vulnerability classified under CWE-226, which pertains to sensitive information not being properly removed before resource reuse. In this case, the Neo4j graph database's Bolt protocol handshake process in both Enterprise and Community editions (versions 5.26.0 and 2025.1.0) leaks one byte of information from previous connections. This occurs because the server reuses memory buffers without clearing sensitive data, allowing an attacker to glean residual data during the handshake. The attacker does not have control over the leaked byte, limiting the direct usefulness of the information. The vulnerability is remotely exploitable without authentication or user interaction, increasing its risk profile. The CVSS 4.0 score is 6.3 (medium severity), reflecting the limited impact and scope. No patches or known exploits are currently available, but the flaw could be leveraged in multi-stage attacks or to infer sensitive server state. The leak affects confidentiality but not integrity or availability. The Bolt protocol is a core communication channel for Neo4j clients, so exposure of this channel to untrusted networks increases risk. Organizations using Neo4j in sensitive environments should consider this vulnerability in their threat models.

For European organizations, the primary impact is a minor confidentiality breach where an attacker can obtain residual data from previous Neo4j connections. While the leak is limited to one byte and the attacker cannot control the content, this could potentially aid in reconnaissance or be combined with other vulnerabilities to escalate attacks. Organizations relying on Neo4j for critical data processing, such as financial institutions, telecommunications, or government agencies, may face increased risk if the Bolt protocol is exposed to untrusted networks. The vulnerability does not affect data integrity or availability, so direct disruption or data manipulation is unlikely. However, the presence of any information leak in a database system handling sensitive or regulated data (e.g., GDPR-protected personal data) could have compliance implications. The lack of authentication requirement means attackers can attempt exploitation remotely, increasing the threat surface. Overall, the impact is moderate but should not be ignored in high-security environments.

1. Restrict network access to Neo4j Bolt protocol endpoints by implementing strict firewall rules and network segmentation to limit exposure to trusted clients only. 2. Monitor Neo4j vendor communications closely for patches or updates addressing CVE-2025-11602 and apply them promptly once available. 3. Employ encrypted VPN tunnels or secure network channels for all Neo4j client-server communications to reduce the risk of interception or exploitation. 4. Conduct regular security audits and memory management reviews in Neo4j deployments to detect potential residual data leaks. 5. Use application-layer controls to limit the number of concurrent connections and handshake attempts, reducing the attack surface. 6. Consider deploying intrusion detection systems (IDS) or anomaly detection tools to identify unusual handshake patterns or repeated connection attempts. 7. If feasible, upgrade to Neo4j versions not affected by this vulnerability once patches are released. 8. Document and review data classification and handling policies to ensure that any leaked data byte does not expose sensitive information.