CVE-2018-11615 in mosca
Summary
by MITRE
This vulnerability allows remote attackers to deny service on vulnerable installations of npm mosca 2.8.1. Authentication is not required to exploit this vulnerability. The specific flaw exists within the processing of topics. A crafted regular expression can cause the broker to crash. An attacker can leverage this vulnerability to deny access to the target system. Was ZDI-CAN-6306.
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Analysis
by VulDB Data Team • 03/19/2020
The vulnerability identified as CVE-2018-11615 represents a critical denial of service flaw in npm mosca version 2.8.1, a popular MQTT broker implementation written in javascript. This vulnerability operates at the application layer and specifically targets the message broker's topic processing functionality, making it particularly dangerous as it can be exploited remotely without any authentication requirements. The flaw resides in how the system handles topic subscriptions and pattern matching, creating a scenario where malicious input can trigger system instability and complete service disruption.
The technical root cause of this vulnerability stems from inadequate input validation within the topic handling mechanism of the mosca broker. When processing topic subscriptions, the system employs regular expression matching to determine subscription patterns, but fails to properly sanitize or limit the complexity of these patterns. An attacker can craft a specially designed regular expression that, when processed by the broker, causes a catastrophic failure in the regular expression engine. This particular vulnerability manifests as a regular expression denial of service attack, where the malicious pattern causes the system to enter an infinite loop or consume excessive computational resources during pattern matching operations.
The operational impact of this vulnerability extends far beyond simple service disruption, as it can be leveraged by attackers to create persistent availability issues for mqtt-based systems. In environments where mosca brokers serve as critical infrastructure for IoT deployments, industrial automation, or real-time messaging systems, this vulnerability can lead to complete service outages that affect numerous connected devices and applications. The attack vector is particularly concerning because it requires no authentication credentials, making it accessible to any remote attacker with network access to the vulnerable system. This characteristic aligns with attack patterns documented in the mitre att&ck framework under the service stop category, where adversaries seek to disrupt system availability through resource exhaustion or process termination.
From a security standards perspective, this vulnerability maps directly to CWE-400, which covers "Uncontrolled Resource Consumption" and specifically addresses regular expression denial of service conditions. The flaw also demonstrates characteristics consistent with CWE-20, "Improper Input Validation," as the system fails to properly validate or sanitize user-supplied topic patterns before processing them. Organizations utilizing mosca brokers in production environments face significant risk from this vulnerability, as the impact can cascade through dependent systems that rely on the mqtt messaging infrastructure. The vulnerability's classification as a remote unauthenticated attack makes it particularly attractive to threat actors seeking to disrupt services without requiring privileged access or complex exploitation techniques.
Mitigation strategies for this vulnerability should prioritize immediate patching of affected mosca installations to version 2.8.2 or later, which contains the necessary fixes for the regular expression processing logic. Network administrators should implement monitoring solutions to detect unusual patterns in topic subscription requests that might indicate exploitation attempts. Additionally, organizations should consider implementing rate limiting and input validation measures at network boundaries to prevent malicious topic patterns from reaching the broker. The remediation approach should also include comprehensive security assessments of all mqtt-based systems within the organization's infrastructure to identify potential similar vulnerabilities in other messaging components.