CVE-2019-17056 in Linux
Summary
by MITRE
llcp_sock_create in net/nfc/llcp_sock.c in the AF_NFC network module in the Linux kernel through 5.3.2 does not enforce CAP_NET_RAW, which means that unprivileged users can create a raw socket, aka CID-3a359798b176.
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Analysis
by VulDB Data Team • 12/29/2023
The vulnerability identified as CVE-2019-17056 represents a critical privilege escalation flaw within the Linux kernel's NFC (Near Field Communication) subsystem. This issue exists in the llcp_sock_create function located in net/nfc/llcp_sock.c, which is part of the AF_NFC network module. The vulnerability allows unprivileged users to bypass the expected security controls that should restrict raw socket creation to processes with appropriate privileges, specifically the CAP_NET_RAW capability. This represents a significant deviation from the kernel's privilege model where raw socket creation should be restricted to users with elevated permissions to prevent potential misuse of network interfaces.
The technical flaw stems from the improper enforcement of the CAP_NET_RAW capability check within the NFC subsystem's socket creation logic. When a user attempts to create a raw socket through the NFC interface, the kernel fails to validate whether the requesting process possesses the necessary network raw socket permissions. This oversight creates a pathway for any local user to establish raw network connections without proper authorization, effectively circumventing the kernel's security boundaries that typically protect against unauthorized access to low-level network operations. The vulnerability specifically affects Linux kernel versions through 5.3.2, indicating that this flaw was present in a substantial portion of the kernel's release cycle and likely impacted numerous production systems.
From an operational perspective, this vulnerability enables unprivileged users to potentially perform network reconnaissance, conduct man-in-the-middle attacks, or manipulate NFC communications in ways that could compromise system security. The ability to create raw sockets through NFC interfaces opens possibilities for network traffic interception, spoofing, or other malicious activities that would typically require administrative privileges. The impact extends beyond simple privilege escalation as it provides attackers with a means to interact with NFC hardware at a level that could expose sensitive data or disrupt NFC-based services. This vulnerability particularly affects systems that utilize NFC functionality, including mobile devices, IoT appliances, and any hardware that relies on NFC for communication protocols.
The security implications of this vulnerability align with CWE-276, which addresses improper privileges, and can be mapped to ATT&CK technique T1068, which involves exploiting privileges to gain elevated access. Organizations should implement immediate mitigations including kernel updates to versions that address this vulnerability, proper access controls to limit local user privileges, and monitoring for unauthorized raw socket creation attempts. System administrators should also consider disabling NFC functionality when not required, implementing network segmentation to limit NFC communication scope, and conducting regular security audits to detect potential exploitation attempts. The vulnerability demonstrates the importance of maintaining strict privilege enforcement across all kernel subsystems and highlights the need for comprehensive security testing of network interfaces and device drivers to prevent similar issues in other kernel modules.