CVE-2017-2891 in Mongoose
Summary
by MITRE
An exploitable use-after-free vulnerability exists in the HTTP server implementation of Cesanta Mongoose 6.8. An ordinary HTTP POST request with a CGI target can cause a reuse of previously freed pointer potentially resulting in remote code execution. An attacker needs to send this HTTP request over the network to trigger this vulnerability.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 01/06/2023
The vulnerability identified as CVE-2017-2891 represents a critical use-after-free condition within the Cesanta Mongoose HTTP server version 6.8, classified under CWE-416 as Use of Freed Memory. This flaw exists in the server's implementation of HTTP POST request handling when processing CGI targets, creating a scenario where memory management errors can be exploited by remote attackers. The vulnerability stems from improper memory deallocation practices within the server's request processing pipeline, specifically when handling dynamic content through CGI interfaces. The flaw allows an attacker to manipulate memory state through crafted HTTP requests, potentially leading to arbitrary code execution on the affected system.
The technical exploitation mechanism involves sending a specially crafted HTTP POST request to a CGI endpoint, which triggers the server to free memory associated with a pointer while still maintaining references to it. When the server attempts to reuse this freed memory location, the attacker can potentially control the data that gets written to the freed memory space. This memory corruption allows for the execution of arbitrary code with the privileges of the web server process, effectively providing a remote code execution capability. The vulnerability is particularly dangerous because it requires no authentication or privileged access, making it exploitable over the network by any remote attacker who can send HTTP requests to the target server.
The operational impact of this vulnerability extends beyond simple remote code execution, as it can enable complete system compromise when the web server is running with elevated privileges. An attacker exploiting this vulnerability could gain access to sensitive data, establish persistent backdoors, or use the compromised system as a launch point for further attacks within the network infrastructure. The attack surface is broad since any system running Cesanta Mongoose 6.8 with CGI support enabled is potentially vulnerable, including web applications, embedded systems, and IoT devices that utilize this HTTP server implementation. The vulnerability also aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter, as successful exploitation would allow attackers to execute commands on the compromised system through the CGI interface.
Mitigation strategies for CVE-2017-2891 should prioritize immediate patching of the Cesanta Mongoose server to version 6.9 or later, where the memory management issues have been resolved. Organizations should also implement network segmentation and access controls to limit exposure of vulnerable systems to untrusted networks. Additional defensive measures include monitoring for suspicious HTTP POST requests, particularly those targeting CGI endpoints, and implementing web application firewalls to detect and block malformed requests that could trigger the vulnerability. Security teams should also consider disabling CGI support on web servers where it is not strictly required, as this reduces the attack surface. The vulnerability demonstrates the critical importance of proper memory management in server implementations and highlights the necessity of regular security updates and vulnerability assessments for all network services, particularly those handling user input through HTTP protocols.