CVE-2026-82064 in MongoDB
Summary
by MITRE • 09/08/2026
A security issue in MongoDB Server allows an unauthenticated network user to cause a denial of service on a specific type of replica set member. The server contains an assertion in its read concern processing logic that can be reached without authentication, and the assertion's assumptions about internal state do not hold for all member configurations, causing the server process to terminate.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 09/08/2026
The vulnerability identified in MongoDB Server represents a critical denial of service condition stemming from insufficient input validation within the database engine's read concern processing logic. This flaw specifically affects replica set deployments where an unauthenticated network user can interact with specific types of member nodes, such as secondary or arbiter members, to trigger the fault. The core technical issue lies in an assertion statement that assumes a particular internal state configuration which is not universally valid across all possible replica set topologies and operational states. When this assumption fails due to the complex interplay between replication synchronization and read concern parameters, the server process abruptly terminates rather than handling the error gracefully or returning a standard database error code.
From an architectural perspective, MongoDB relies heavily on assertions during development and testing phases to catch logical errors early in the software lifecycle. However, in production builds, these assertions are often retained for critical path validations but must be designed to handle edge cases robustly without causing system crashes. In this instance, the assertion does not adequately account for scenarios where a replica set member is undergoing state transitions or has specific configuration attributes that differ from the standard primary node behavior. An attacker can exploit this by crafting network requests with specific read concern parameters that force the server into an unexpected internal state, thereby triggering the fatal assertion and causing immediate process termination.
The operational impact of this vulnerability is severe for organizations relying on high availability through MongoDB replica sets. Since the attack requires no authentication, it allows any remote actor to disrupt service by targeting accessible endpoints. The resulting denial of service leads to complete unavailability of the affected database instance until manual intervention restarts the server process. In a clustered environment, while other nodes may continue operating if they are not directly targeted or if failover mechanisms activate correctly, the loss of a critical node can degrade performance, increase latency for remaining clients, and potentially lead to data inconsistency during the recovery period depending on the quorum status at the time of the crash.
This vulnerability aligns with CWE-20 Improper Input Validation as it involves failing to properly validate inputs that influence internal state assumptions. Furthermore, from a threat modeling perspective consistent with MITRE ATT&CK frameworks, this falls under T1499 Endpoint Denial of Service or potentially T1529 System Shutdown/Reboot if the crash leads to automatic restarts causing service interruption. The lack of authentication requirement places it in the category of attacks that can be executed remotely without prior compromise, significantly lowering the barrier for exploitation by malicious actors seeking to disrupt services.
Mitigation strategies must focus on both immediate remediation and long-term architectural hardening. MongoDB has addressed this issue through software updates that modify the read concern processing logic to handle edge cases in replica set configurations more robustly. Administrators should immediately apply the latest security patches provided by MongoDB for their specific version of the server. Additionally, network-level controls such as firewalls or access control lists can be configured to restrict direct access to database ports from untrusted networks until patching is complete. For environments where immediate patching is not feasible, disabling read concern features that trigger the vulnerability may serve as a temporary workaround, although this could impact application functionality requiring specific consistency guarantees. Regular auditing of replica set configurations and ensuring all members are running supported versions with current security fixes is essential to prevent recurrence.