CVE-2019-20925 in MongoDB
Summary
by MITRE • 11/24/2020
An unauthenticated client can trigger denial of service by issuing specially crafted wire protocol messages, which cause the message decompressor to incorrectly allocate memory. This issue affects: MongoDB Inc. MongoDB Server v4.2 versions prior to 4.2.1; v4.0 versions prior to 4.0.13; v3.6 versions prior to 3.6.15; v3.4 versions prior to 3.4.24.
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Analysis
by VulDB Data Team • 09/17/2024
This vulnerability represents a critical denial of service flaw in MongoDB server implementations that stems from improper handling of wire protocol messages during decompression operations. The issue manifests when unauthenticated clients can exploit a memory allocation error in the message decompressor component, allowing them to trigger a denial of service condition without requiring any authentication credentials. The vulnerability affects multiple major versions of MongoDB including 4.2 prior to 4.2.1, 4.0 prior to 4.0.13, 3.6 prior to 3.6.15, and 3.4 prior to 3.4.24, indicating a widespread impact across the MongoDB ecosystem. From a cybersecurity perspective, this vulnerability aligns with CWE-129, which addresses improper validation of length fields, and represents a classic example of a resource exhaustion attack vector that can be exploited by malicious actors to disrupt service availability.
The technical mechanism behind this vulnerability involves the manipulation of wire protocol messages that are processed by the MongoDB server's decompression subsystem. When malformed or specially crafted messages are received, the decompressor logic fails to properly validate the memory allocation requirements, potentially leading to excessive memory consumption or allocation failures. This type of vulnerability falls under the ATT&CK technique T1499.004, which covers "Endpoint Denial of Service" through resource exhaustion attacks. The flaw essentially allows an attacker to consume system resources in a way that prevents legitimate operations from completing successfully, effectively creating a denial of service condition that can impact database availability and application functionality.
The operational impact of this vulnerability extends beyond simple service disruption as it can affect database performance, application reliability, and overall system availability for organizations running affected MongoDB versions. Organizations may experience unexpected downtime, degraded performance, or complete service unavailability when exploited, particularly in environments where MongoDB serves as a critical backend component for applications. The unauthenticated nature of the attack means that any client capable of connecting to the MongoDB service can potentially exploit this vulnerability, making it particularly dangerous in environments where network access controls are not properly implemented. Security teams must consider this vulnerability as part of their broader denial of service attack surface and implement appropriate monitoring and mitigation strategies.
Organizations should prioritize immediate patching of affected MongoDB versions to address this vulnerability, with the recommended approach being to upgrade to the patched versions mentioned in the CVE description. System administrators should also implement network segmentation and access controls to limit exposure of MongoDB services to untrusted networks, while monitoring for unusual patterns of connection attempts or resource consumption that might indicate exploitation attempts. Additionally, implementing proper input validation and resource monitoring can help detect and mitigate potential exploitation attempts, as the vulnerability specifically targets memory allocation behavior during message processing. The fix for this vulnerability typically involves proper validation of message length fields and improved memory allocation handling within the decompression logic, ensuring that malformed messages cannot trigger excessive resource consumption or allocation failures that lead to denial of service conditions.