CVE-2017-7295 in Operating System
Summary
by MITRE
An issue was discovered in Contiki Operating System 3.0. A use-after-free vulnerability exists in httpd-simple.c in cc26xx-web-demo httpd, where upon a connection close event, the http_state structure was not deallocated properly, resulting in a NULL pointer dereference in the output processing function. This resulted in a board crash, which can be used to perform denial of service.
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Analysis
by VulDB Data Team • 10/03/2020
The vulnerability identified as CVE-2017-7295 represents a critical use-after-free flaw within the Contiki Operating System version 3.0, specifically affecting the cc26xx-web-demo httpd implementation. This issue manifests in the httpd-simple.c file where improper memory management during connection termination events creates a dangerous condition that can be exploited by adversaries. The flaw occurs when a network connection is closed, yet the http_state structure remains in an inconsistent state, leading to subsequent memory access violations that compromise system stability.
The technical execution of this vulnerability involves a classic use-after-free scenario where memory allocated to the http_state structure is freed but not properly nullified, allowing subsequent code paths to reference freed memory locations. When the output processing function attempts to access this freed structure, it encounters a NULL pointer dereference that ultimately results in a complete system crash or board reboot. This memory management error directly aligns with CWE-416, which categorizes use-after-free conditions as a fundamental flaw in memory handling practices. The vulnerability demonstrates poor resource management where the developer failed to implement proper cleanup routines that would ensure memory deallocation occurs safely without leaving dangling pointers.
From an operational perspective, this vulnerability presents a significant denial of service threat to embedded systems running the affected Contiki version. The board crash resulting from this flaw can be triggered remotely through normal network connection termination sequences, making it particularly dangerous in networked environments where devices may be exposed to untrusted clients. The impact extends beyond simple service disruption as the system instability could potentially compromise other running processes or lead to more severe system failures. This vulnerability falls under ATT&CK technique T1499.004, specifically targeting network denial of service through system resource exhaustion or corruption, and represents a critical weakness in embedded system security architecture.
The mitigation strategies for CVE-2017-7295 require immediate implementation of proper memory management practices within the Contiki OS framework. System administrators should prioritize updating to patched versions of Contiki OS where the memory deallocation logic has been corrected to properly nullify pointers after deallocation. Additionally, implementing proper input validation and connection state management can help prevent exploitation of similar memory corruption vulnerabilities. The fix should ensure that when httpd connections are closed, all associated memory structures are properly freed and any references are reset to prevent subsequent access attempts. Organizations should also consider implementing network segmentation and monitoring to detect anomalous connection termination patterns that may indicate exploitation attempts, while maintaining regular security updates to address similar vulnerabilities in embedded operating systems.