CVE-2025-7259 is a medium-severity vulnerability identified in MongoDB Server version 8.1.0, classified under CWE-843 (Access of Resource Using Incompatible Type, commonly known as 'Type Confusion'). This vulnerability arises when an authorized user issues queries containing duplicate _id fields, which leads to unexpected behavior in the MongoDB Server. Specifically, the server may crash, resulting in a Denial of Service (DoS) condition. The root cause is the server's improper handling of queries with conflicting or incompatible type information in the _id field, which is a critical identifier in MongoDB documents. Since the issue requires an authorized user to trigger it, exploitation is limited to users with legitimate access to the database. The vulnerability does not affect confidentiality or integrity but impacts availability by causing server crashes. The CVSS v3.1 base score is 6.5, reflecting a medium severity level, with the vector indicating network attack vector (AV:N), low attack complexity (AC:L), requiring privileges (PR:L), no user interaction (UI:N), unchanged scope (S:U), no impact on confidentiality or integrity (C:N/I:N), and high impact on availability (A:H). No known exploits are currently reported in the wild, and no patches have been linked yet, indicating that remediation may still be pending or in progress. This vulnerability highlights the importance of input validation and type safety in database query processing to prevent service disruption.

For European organizations relying on MongoDB Server 8.1.0, this vulnerability poses a risk primarily to service availability. A successful exploitation by an authorized user could cause unexpected server crashes, leading to downtime of critical applications and services dependent on MongoDB databases. This could disrupt business operations, especially for sectors with high database transaction volumes such as finance, healthcare, e-commerce, and public services. Although the vulnerability does not allow data leakage or unauthorized data modification, the denial of service could indirectly affect data availability and operational continuity. Organizations with multi-tenant environments or shared database access may face increased risk if an insider or compromised account triggers the vulnerability. The requirement for authorized access limits the attack surface but does not eliminate risk, especially in environments with weak internal access controls or compromised credentials. Additionally, the lack of a patch at the time of disclosure means organizations must rely on mitigating controls until an official fix is available.

1. Restrict database access strictly to trusted and necessary users, enforcing the principle of least privilege to minimize the number of authorized users who could exploit this vulnerability. 2. Implement robust monitoring and anomaly detection on MongoDB query patterns to detect unusual queries, such as those containing duplicate _id fields, which may indicate exploitation attempts. 3. Use network segmentation and firewall rules to limit access to MongoDB servers only from trusted application servers and administrative hosts. 4. Regularly audit user privileges and revoke unnecessary or outdated access rights to reduce the risk of insider threats. 5. Until an official patch is released, consider deploying MongoDB instances in high-availability configurations with failover capabilities to minimize downtime in case of crashes. 6. Engage with MongoDB support or follow official advisories closely to apply patches or updates promptly once available. 7. Conduct internal penetration testing and fuzzing focused on query inputs to identify and mitigate similar input validation issues proactively.