CVE-2017-8824 in Linux
Summary
by MITRE
The dccp_disconnect function in net/dccp/proto.c in the Linux kernel through 4.14.3 allows local users to gain privileges or cause a denial of service (use-after-free) via an AF_UNSPEC connect system call during the DCCP_LISTEN state.
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Analysis
by VulDB Data Team • 12/21/2024
The vulnerability identified as CVE-2017-8824 represents a critical use-after-free condition within the Linux kernel's Datagram Congestion Control Protocol implementation. This flaw exists in the dccp_disconnect function located in net/dccp/proto.c and affects Linux kernel versions through 4.14.3. The vulnerability manifests when a local user executes an AF_UNSPEC connect system call while the DCCP socket is in the LISTEN state, creating a scenario where memory that has already been freed is accessed, leading to unpredictable behavior and potential privilege escalation.
The technical root cause of this vulnerability stems from improper memory management during the disconnect process of DCCP sockets. When a DCCP socket transitions from LISTEN to disconnect state, the kernel fails to properly validate the socket state before attempting to free associated memory structures. The AF_UNSPEC connect system call, which is typically used to specify an unspecified address family, becomes a vector for exploitation when invoked during the specific LISTEN state transition. This improper state handling creates a window where memory deallocation occurs followed by subsequent access to the same memory region, resulting in the use-after-free condition that can be leveraged by malicious local users.
The operational impact of this vulnerability extends beyond simple denial of service to encompass potential privilege escalation capabilities. Local attackers can exploit this condition to execute arbitrary code with elevated privileges, potentially compromising the entire system. The use-after-free vulnerability allows attackers to manipulate heap memory, potentially leading to code execution or system crashes that could be exploited for privilege escalation. The vulnerability affects systems running Linux kernel versions through 4.14.3, making it particularly concerning for organizations that have not yet updated their kernel versions. This issue demonstrates the critical importance of proper memory management in kernel space, where errors can have far-reaching consequences for system security and stability.
Mitigation strategies for CVE-2017-8824 primarily focus on kernel updates and system hardening measures. Organizations should immediately upgrade to Linux kernel versions 4.14.4 or later, where the vulnerability has been patched through proper memory management implementation. The fix addresses the improper state validation during socket disconnect operations and ensures that memory deallocation occurs only when the socket is in a valid state. System administrators should also implement monitoring solutions to detect unusual network activity patterns that might indicate exploitation attempts. Additionally, the vulnerability aligns with CWE-416, which describes the use of freed memory condition, and can be mapped to ATT&CK technique T1068, which covers local privilege escalation through kernel exploits. The vulnerability underscores the necessity of thorough code review and testing of kernel components, particularly those handling socket operations and memory management, to prevent similar issues in future implementations.