CVE-2020-6016 in Game Networking Sockets
Summary
by MITRE • 11/18/2020
Valve's Game Networking Sockets prior to version v1.2.0 improperly handles unreliable segments with negative offsets in function SNP_ReceiveUnreliableSegment(), leading to a Heap-Based Buffer Underflow and a free() of memory not from the heap, resulting in a memory corruption and probably even a remote code execution.
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Analysis
by VulDB Data Team • 12/08/2020
The vulnerability identified as CVE-2020-6016 affects Valve's Game Networking Sockets library, a networking framework used by numerous gaming applications and services. This issue manifests in versions prior to v1.2.0 where the SNP_ReceiveUnreliableSegment() function fails to properly validate incoming network data segments. The flaw specifically occurs when processing unreliable network segments that contain negative offset values, creating a dangerous condition that can be exploited by remote attackers. The vulnerability falls under the category of heap-based buffer underflow, which represents a critical class of memory safety issues that can lead to arbitrary code execution.
The technical implementation of this vulnerability stems from inadequate input validation within the network packet processing pipeline. When the SNP_ReceiveUnreliableSegment() function receives a malformed packet containing negative offset values, the code fails to properly bounds-check these values before using them to calculate memory access offsets. This improper handling results in memory corruption where the application attempts to read from memory locations that are outside the intended buffer boundaries. The underflow condition causes the program to access memory that may not belong to the heap, leading to a scenario where free() is called on memory that was not allocated through the standard heap allocation mechanisms. This fundamental violation of memory management principles creates a predictable crash condition that can be leveraged for more sophisticated attacks.
The operational impact of this vulnerability extends beyond simple application instability to potentially enable remote code execution in affected systems. Attackers can craft malicious network packets with negative offset values that trigger the buffer underflow condition when processed by vulnerable applications. The memory corruption resulting from this condition can be exploited to overwrite critical memory structures, potentially allowing attackers to execute arbitrary code with the privileges of the affected application. This risk is particularly severe in gaming environments where applications often run with elevated privileges or have access to system resources that could be leveraged for further exploitation. The vulnerability affects not just individual games but entire networking frameworks that rely on Valve's Game Networking Sockets library, creating a wide attack surface across multiple applications and services.
Mitigation strategies for CVE-2020-6016 primarily focus on updating to the patched version v1.2.0 or later, which includes proper bounds checking and input validation for network segments. Organizations should prioritize patching affected applications that utilize Valve's Game Networking Sockets library, particularly those deployed in production environments or serving external network traffic. Network segmentation and firewall rules can provide additional protection by limiting access to vulnerable services and reducing the attack surface. The vulnerability aligns with CWE-129, which covers insufficient validation of array index values, and can be mapped to ATT&CK technique T1203, representing legitimate user execution through exploitation of a vulnerability in a system or application. Security monitoring should focus on detecting anomalous network traffic patterns that might indicate exploitation attempts, including unusual packet structures or unexpected memory access patterns in affected applications.