CVE-2018-20355 in Mongoose Embedded Web Server Library
Summary
by MITRE
An invalid write of 8 bytes due to a use-after-free vulnerability in the mg_http_free_proto_data_cgi function call in mongoose.c in Cesanta Mongoose Embedded Web Server Library 6.13 and earlier allows a denial of service (application crash) or remote code execution.
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Analysis
by VulDB Data Team • 10/03/2023
The vulnerability identified as CVE-2018-20355 represents a critical use-after-free condition within the Cesanta Mongoose Embedded Web Server Library version 6.13 and earlier. This flaw manifests in the mg_http_free_proto_data_cgi function where an invalid write operation of 8 bytes occurs, creating a potential vector for both denial of service and remote code execution attacks. The issue arises from improper memory management where freed memory regions are accessed or overwritten, leading to unpredictable application behavior and system instability. The vulnerability specifically affects embedded web server implementations that utilize the mongoose.c library, making it particularly concerning for IoT devices, embedded systems, and network appliances that rely on this web server component for their functionality.
The technical exploitation of this vulnerability involves manipulating HTTP requests to trigger the use-after-free condition within the mg_http_free_proto_data_cgi function. When the web server processes certain malformed HTTP protocol data, it attempts to free memory resources that are subsequently accessed or written to, causing either an application crash or potentially allowing an attacker to execute arbitrary code on the target system. This type of vulnerability falls under CWE-416, which specifically addresses the use of freed memory conditions in software applications. The memory corruption occurs during the protocol data handling phase of HTTP request processing, where the library fails to properly validate or manage the lifecycle of allocated memory resources, creating opportunities for attackers to manipulate the execution flow.
The operational impact of CVE-2018-20355 extends beyond simple service disruption to encompass potential system compromise and unauthorized access. Organizations deploying affected versions of the Cesanta Mongoose library face risks including persistent denial of service attacks that can render devices unavailable to legitimate users, as well as remote code execution that could allow attackers to gain complete control over affected systems. This vulnerability is particularly dangerous in embedded environments where devices may not receive regular security updates, creating persistent attack surfaces that can be exploited by threat actors. The impact is amplified in Internet of Things deployments where multiple devices may be vulnerable and could be orchestrated into larger attack campaigns, making this a significant concern for network security and device management.
Mitigation strategies for CVE-2018-20355 require immediate action to upgrade to patched versions of the Cesanta Mongoose library, specifically version 6.14 or later where the memory management issues have been resolved. Organizations should conduct comprehensive vulnerability assessments to identify all systems utilizing affected library versions and prioritize remediation efforts accordingly. Network segmentation and access controls can provide additional defense-in-depth measures to limit the potential impact of exploitation attempts. Security monitoring should be enhanced to detect unusual HTTP traffic patterns that might indicate exploitation attempts, while application firewalls can be configured to filter potentially malicious requests. The vulnerability also highlights the importance of secure coding practices and regular security audits, particularly for embedded systems that may not undergo the same rigorous testing as enterprise applications, aligning with ATT&CK technique T1059.007 for command and scripting interpreter usage in exploitation scenarios.