CVE-2018-5703 in Linux
Summary
by MITRE • 01/25/2023
The tcp_v6_syn_recv_sock function in net/ipv6/tcp_ipv6.c in the Linux kernel through 4.14.11 allows attackers to cause a denial of service (slab out-of-bounds write) or possibly have unspecified other impact via vectors involving TLS.
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Analysis
by VulDB Data Team • 01/25/2023
The vulnerability identified as CVE-2018-5703 represents a critical security flaw in the Linux kernel's implementation of IPv6 TCP handling, specifically within the tcp_v6_syn_recv_sock function located in net/ipv6/tcp_ipv6.c. This issue affects Linux kernel versions through 4.14.11 and demonstrates a slab out-of-bounds write condition that can be exploited through TLS-related network traffic patterns. The flaw resides in the kernel's handling of TCP SYN_RECV socket creation for IPv6 connections, particularly when TLS is involved in the communication process. Such vulnerabilities fall under CWE-787, which specifically addresses out-of-bounds write conditions in software systems, making this a serious concern for system administrators and security professionals managing Linux-based infrastructure.
The technical exploitation of this vulnerability occurs when the Linux kernel processes TCP connections over IPv6 networks while TLS encryption is active. During the TCP handshake process, specifically when establishing SYN_RECV sockets for incoming connections, the kernel's IPv6 TCP implementation fails to properly validate input data from TLS-enabled connections. This validation failure results in a situation where attacker-controlled data can overwrite memory locations beyond the intended slab allocation boundaries. The slab out-of-bounds write condition creates opportunities for memory corruption that can lead to system instability or potential privilege escalation. The vulnerability is particularly concerning because it can be triggered through legitimate network traffic patterns involving TLS connections, making detection and prevention challenging.
The operational impact of CVE-2018-5703 extends beyond simple denial of service scenarios, as the slab out-of-bounds write condition could potentially enable more sophisticated attacks. When exploited, this vulnerability can cause system crashes, leading to denial of service conditions that disrupt network services and application availability. In some cases, the memory corruption might provide attackers with opportunities to execute arbitrary code with kernel privileges, though the exact exploitability depends on various system configurations and memory layout conditions. The vulnerability affects systems running Linux kernel versions up to 4.14.11, which includes many enterprise and server deployments that rely on stable kernel versions for production environments. Network services such as web servers, database systems, and application servers that handle IPv6 traffic with TLS encryption are particularly at risk.
Mitigation strategies for CVE-2018-5703 primarily focus on kernel version updates and network-level protections. The most effective immediate solution involves upgrading to Linux kernel versions 4.14.12 or later, where the vulnerability has been patched through proper bounds checking in the tcp_v6_syn_recv_sock function. System administrators should prioritize patching affected systems, particularly those handling IPv6 traffic with TLS connections. Network administrators can implement additional protections by monitoring for unusual TCP SYN_RECV socket behavior and implementing rate limiting for incoming connection requests. The ATT&CK framework categorizes this vulnerability under T1499.004, which deals with network denial of service, and T1068, which addresses local privilege escalation through kernel vulnerabilities. Organizations should also consider implementing network segmentation and firewall rules to limit exposure to potentially malicious TLS connections while maintaining operational security through proper incident response procedures and vulnerability management protocols.