CVE-2018-18765 in Mongoose
Summary
by MITRE
An exploitable arbitrary memory read vulnerability exists in the MQTT packet-parsing functionality of Cesanta Mongoose 6.13. It is a heap-based buffer over-read in mg_mqtt_next_subscribe_topic. A specially crafted MQTT SUBSCRIBE packet can cause an arbitrary out-of-bounds memory read potentially resulting in information disclosure and denial of service. An attacker needs to send a specially crafted MQTT packet over the network to trigger this vulnerability.
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Analysis
by VulDB Data Team • 04/07/2020
The vulnerability CVE-2018-18765 represents a critical heap-based buffer over-read flaw in Cesanta Mongoose 6.13's MQTT packet parsing mechanism, specifically within the mg_mqtt_next_subscribe_topic function. This issue arises from inadequate input validation and boundary checking during the processing of MQTT SUBSCRIBE packets, creating a scenario where maliciously crafted network traffic can trigger unauthorized memory access patterns. The vulnerability falls under the CWE-125 weakness category, which encompasses out-of-bounds read conditions that can lead to information disclosure and system instability. The affected component operates at the network protocol parsing layer, making it particularly dangerous as it can be exploited remotely without requiring local system access or authentication credentials.
The technical exploitation of this vulnerability occurs when an attacker crafts a specially formatted MQTT SUBSCRIBE packet that contains malformed topic subscription entries. During the parsing process, the mg_mqtt_next_subscribe_topic function fails to properly validate the length of incoming data structures, leading to a heap-based buffer over-read condition. This flaw allows an attacker to read arbitrary memory locations beyond the intended buffer boundaries, potentially exposing sensitive information such as stack contents, heap metadata, or other process memory segments. The over-read behavior can manifest in various ways including information disclosure of system memory, partial data leakage, or complete memory dumps that may contain cryptographic keys, session tokens, or other confidential information. The vulnerability is classified under the ATT&CK technique T1059.007 for command and scripting interpreter, as it enables remote code execution through information disclosure that can be leveraged for further exploitation.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can also facilitate denial of service conditions by causing application crashes or memory corruption. When exploited successfully, the vulnerability can result in complete system instability, particularly in environments where Mongoose is used as a core networking component for IoT devices, embedded systems, or network services. The remote attack vector makes this vulnerability particularly concerning for internet-facing services, as it requires no privileged access or local system compromise. Organizations using Cesanta Mongoose 6.13 in production environments face significant risk exposure, especially in scenarios involving MQTT-based communication protocols where unauthorized parties might attempt to inject malicious packets. The vulnerability demonstrates the importance of proper input validation and memory boundary checking in network protocol implementations, as even seemingly benign protocol parsing functions can become attack vectors when insufficiently protected against malformed input data.
Mitigation strategies for CVE-2018-18765 should focus on immediate software updates to patched versions of Cesanta Mongoose, as well as implementing network-level protections such as firewall rules and packet filtering to restrict MQTT traffic from untrusted sources. Organizations should also consider implementing intrusion detection systems that can identify and block suspicious MQTT packet patterns that might indicate exploitation attempts. Additional defensive measures include deploying memory protection mechanisms such as stack canaries, address space layout randomization, and heap integrity checks to reduce the impact of potential exploitation. The vulnerability underscores the necessity of thorough security testing for network protocol implementations and highlights the importance of following secure coding practices that include proper input validation, boundary checking, and memory management. Regular security assessments and vulnerability scanning should be implemented to identify similar issues in other network components and ensure comprehensive protection against similar classes of vulnerabilities.