CVE-2019-3874 in Linux
Summary
by MITRE
The SCTP socket buffer used by a userspace application is not accounted by the cgroups subsystem. An attacker can use this flaw to cause a denial of service attack. Kernel 3.10.x and 4.18.x branches are believed to be vulnerable.
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Analysis
by VulDB Data Team • 08/07/2023
The vulnerability described in CVE-2019-3874 represents a critical resource management flaw within the Linux kernel's implementation of the Stream Control Transmission Protocol. This issue stems from the improper accounting of SCTP socket buffers within the control groups subsystem, which is a fundamental component of Linux containerization and resource isolation. The cgroups subsystem serves as the primary mechanism for limiting, prioritizing, and isolating resource usage by processes and groups of processes, making this flaw particularly dangerous in containerized environments where resource boundaries are strictly enforced. When userspace applications utilize SCTP sockets, the memory allocated for socket buffers should be properly tracked and accounted against the cgroup limits to prevent resource exhaustion attacks.
The technical implementation of this vulnerability occurs at the kernel level where the SCTP subsystem fails to properly integrate with the cgroups memory accounting mechanisms. This misconfiguration allows malicious users to allocate SCTP socket buffers without proper cgroup tracking, effectively bypassing resource limitations that should prevent any single process or group from consuming excessive memory resources. The flaw specifically affects kernel versions 3.10.x and 4.18.x, which were widely deployed across enterprise environments and cloud infrastructure providers. The root cause aligns with CWE-775, which describes the improper handling of resources without proper accounting mechanisms, and represents a classic example of resource leak or exhaustion vulnerability. Attackers can exploit this by creating multiple SCTP socket connections and allocating substantial buffer memory that remains unaccounted within the cgroup limits, gradually consuming system resources until the system becomes unresponsive or crashes.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to potentially compromise entire system stability and availability. In containerized environments, this flaw enables attackers to exhaust memory resources allocated to specific containers or cgroups, effectively causing those containers to become unresponsive or be terminated by the kernel's out-of-memory killer. The vulnerability can be particularly devastating in cloud computing environments where multiple tenants share the same physical infrastructure, as an attacker could consume resources allocated to other users or applications. The attack vector is relatively simple to execute, requiring only standard SCTP socket operations and memory allocation techniques that do not require elevated privileges. This makes the vulnerability highly exploitable in environments where SCTP is actively used, particularly in telecommunications infrastructure, financial services, and other industries that rely on SCTP for reliable message delivery.
Mitigation strategies for CVE-2019-3874 must address both immediate operational concerns and long-term architectural improvements. The most direct solution involves applying kernel patches that properly integrate SCTP socket buffer accounting with the cgroups subsystem, ensuring that all memory allocations are tracked against appropriate resource limits. System administrators should also implement monitoring solutions that can detect unusual memory consumption patterns and alert on potential exploitation attempts. The vulnerability demonstrates the importance of comprehensive resource accounting across all kernel subsystems, particularly those handling network protocols that may be used for resource exhaustion attacks. Organizations should consider implementing additional layers of protection such as network segmentation, rate limiting, and protocol-specific restrictions to prevent unauthorized access to SCTP functionality. This vulnerability also highlights the need for regular kernel updates and security assessments, as it represents a gap in the security model that could be exploited in sophisticated multi-stage attacks. The ATT&CK framework categorizes this as a resource exhaustion technique under the system service compromise category, emphasizing the need for robust resource management and monitoring capabilities to detect and prevent such attacks.