CVE-2016-9793 in Linux
Summary
by MITRE • 01/25/2023
The sock_setsockopt function in net/core/sock.c in the Linux kernel before 4.8.14 mishandles negative values of sk_sndbuf and sk_rcvbuf, which allows local users to cause a denial of service (memory corruption and system crash) or possibly have unspecified other impact by leveraging the CAP_NET_ADMIN capability for a crafted setsockopt system call with the (1) SO_SNDBUFFORCE or (2) SO_RCVBUFFORCE option.
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Analysis
by VulDB Data Team • 11/06/2024
The vulnerability identified as CVE-2016-9793 represents a critical flaw in the Linux kernel's socket implementation that affects versions prior to 4.8.14. This issue resides within the sock_setsockopt function located in net/core/sock.c, which handles socket option configuration operations. The vulnerability specifically targets the improper handling of negative values for socket send and receive buffer sizes, creating a potential pathway for privilege escalation and system instability. The flaw is particularly dangerous because it can be exploited by local users who possess the CAP_NET_ADMIN capability, making it accessible to processes with network administration privileges.
The technical nature of this vulnerability stems from the kernel's failure to properly validate socket buffer size parameters when processing SO_SNDBUFFORCE and SO_RCVBUFFORCE options. When negative values are passed to these socket options, the kernel's buffer management logic becomes corrupted, leading to memory allocation errors and potential kernel crashes. This occurs because the kernel's internal buffer size calculations do not account for negative values, causing arithmetic overflow conditions and invalid memory access patterns. The improper validation allows malicious actors to manipulate socket buffer parameters in ways that bypass normal kernel safety mechanisms.
Operationally, this vulnerability presents significant risks to system stability and availability. Local attackers with CAP_NET_ADMIN privileges can trigger memory corruption that results in system crashes and denial of service conditions. The impact extends beyond simple system instability, as the memory corruption can potentially lead to privilege escalation or arbitrary code execution within kernel space. This makes the vulnerability particularly dangerous in multi-user environments or systems where network administration capabilities are granted to less privileged users. The exploitation requires minimal privileges but can cause substantial damage to system operations and data integrity.
Mitigation strategies for CVE-2016-9793 focus primarily on kernel version updates, as the most effective solution involves upgrading to Linux kernel version 4.8.14 or later where the vulnerability has been patched. System administrators should prioritize patching affected systems, particularly those running older kernel versions that remain vulnerable to this issue. Additional protective measures include restricting CAP_NET_ADMIN capabilities to only essential processes and users, implementing proper access controls, and monitoring for unusual socket configuration activities. Security teams should also consider implementing network segmentation and privilege separation to limit the potential impact of exploitation. This vulnerability aligns with CWE-129, which addresses improper validation of buffer sizes, and maps to ATT&CK technique T1068, which covers local privilege escalation through kernel vulnerabilities. Organizations should conduct thorough vulnerability assessments to identify systems running affected kernel versions and ensure complete remediation across their infrastructure.