CVE-2026-96746 in C Driver
Summary
by MITRE • 09/24/2026
An out-of-bounds write in the connection-monitoring logic of the MongoDB C Driver may allow an unauthenticated party who controls name resolution and the responses of the hosts named in a client's connection string to write beyond the end of a heap buffer. This may cause the application using the driver to terminate unexpectedly.
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Analysis
by VulDB Data Team • 09/24/2026
The vulnerability identified as CVE-2024-31658 represents a critical memory safety issue within the MongoDB C Driver, specifically located in its connection-monitoring logic. This flaw is classified under CWE-787: Out-of-bounds Write, which describes a scenario where software writes data to a memory location beyond the intended boundary of a buffer. The root cause lies in how the driver handles dynamic host resolution and subsequent state management during the establishment or maintenance of connections to MongoDB instances. When an application utilizes this driver, it typically provides a connection string that includes one or more hostname entries representing potential database servers. During operation, the driver performs DNS lookups for these hosts and maintains internal data structures to track their status and connectivity health. The defect arises when processing responses from name resolution services, where improper bounds checking allows an attacker-controlled input to trigger a write operation that exceeds the allocated heap buffer size.
The operational impact of this vulnerability is significant due to its potential for denial-of-service attacks against applications relying on the MongoDB C Driver. An unauthenticated adversary who controls the local network's DNS infrastructure or can manipulate name resolution responses, such as through DNS spoofing or cache poisoning, can exploit this flaw. By providing specifically crafted hostname resolutions that trigger the out-of-bounds write condition, the attacker forces the driver to corrupt adjacent memory regions on the heap. This memory corruption typically leads to immediate application termination via a segmentation fault or similar crash mechanism. While the primary observed impact is availability loss through process crashes, such memory corruption vulnerabilities can sometimes be leveraged for more severe outcomes depending on the specific execution context and compiler protections in place, potentially leading to arbitrary code execution if an attacker can precisely control the overwritten data and heap layout.
From a threat modeling perspective, this vulnerability aligns with MITRE ATT&CK technique T1078: Valid Accounts or related network manipulation techniques where attackers intercept or modify traffic to exploit client-side software flaws. The attack vector requires the adversary to have influence over name resolution services accessible by the victim application, which often implies access to local networks or compromised DNS servers rather than direct remote exploitation from the public internet without intermediate steps. This constraint makes it a medium-complexity attack that relies on environmental factors and network positioning rather than simple remote code execution vectors.
Mitigation strategies for this vulnerability focus primarily on software updates and architectural hardening. The most effective remediation is to upgrade the MongoDB C Driver to a version where the connection-monitoring logic has been patched with proper bounds checking and input validation mechanisms. Organizations should ensure that their dependency management systems are configured to automatically detect and apply security patches for third-party libraries like libmongocrypt or the core driver components. Additionally, implementing network segmentation can reduce the risk by isolating application servers from untrusted DNS resolvers. Deploying host-based intrusion detection systems that monitor for abnormal memory access patterns may also provide early warning indicators of exploitation attempts in environments where immediate patching is not feasible.