CVE-2023-4569 in Linux
Summary
by MITRE • 08/29/2023
A memory leak flaw was found in nft_set_catchall_flush in net/netfilter/nf_tables_api.c in the Linux Kernel. This issue may allow a local attacker to cause a double-deactivations of catchall elements, which results in a memory leak.
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Analysis
by VulDB Data Team • 09/22/2023
The vulnerability identified as CVE-2023-4569 represents a critical memory management flaw within the Linux kernel's netfilter subsystem, specifically in the nft_set_catchall_flush function located at net/netfilter/nf_tables_api.c. This memory leak vulnerability stems from improper handling of catchall elements during the flush operation, creating a scenario where the kernel fails to correctly manage memory resources when processing network filter rules. The flaw manifests when the system attempts to deactivate catchall elements, leading to a condition where memory allocated for these elements is not properly released back to the system. This issue primarily affects systems running Linux kernel versions that include the problematic nftables implementation, potentially exposing systems to gradual memory exhaustion over time.
The technical root cause of this vulnerability lies in the improper double-deactivation of catchall elements within the netfilter framework, which is a core component of Linux networking stack responsible for packet filtering and manipulation. When the nft_set_catchall_flush function processes the removal of catchall elements, it fails to correctly track the state of these elements, resulting in memory that should be deallocated being retained in memory. This condition creates a memory leak that can accumulate over time, particularly when network filter rules are frequently modified or when the system handles high volumes of network traffic. The flaw operates at the kernel level, making it particularly dangerous as it can affect system stability and performance without requiring elevated privileges to exploit.
From an operational perspective, this memory leak vulnerability poses significant risks to system availability and stability, especially in environments where network filtering is heavily utilized such as firewalls, routers, and network security appliances. A local attacker with access to the system can exploit this vulnerability by repeatedly triggering the flush operation on nftables rules, causing progressive memory consumption that can eventually lead to system slowdowns or complete memory exhaustion. The impact extends beyond simple resource consumption as it can potentially cause the kernel to become unresponsive or trigger kernel oops conditions, leading to system crashes. This vulnerability is particularly concerning in server environments where continuous network filtering operations are performed, as the memory leak can compound over time and degrade system performance until manual intervention is required.
Mitigation strategies for CVE-2023-4569 should focus on immediate kernel updates to versions that contain the patched implementation of the nftables API, as provided by the Linux kernel security team. System administrators should prioritize patching affected systems, particularly those running network filtering services, and implement monitoring solutions to detect memory consumption patterns that may indicate exploitation attempts. The vulnerability aligns with CWE-401, which describes improper cleanup of memory resources, and can be categorized under ATT&CK technique T1499.001 for resource exhaustion attacks. Additional defensive measures include implementing rate limiting on nftables operations, monitoring for unusual network filter rule modifications, and conducting regular memory usage audits. Organizations should also consider implementing automated patch management processes to ensure timely deployment of kernel security updates, as this vulnerability can be exploited without requiring network access or special privileges beyond local system access. The long-term mitigation strategy involves maintaining current kernel versions and following security best practices for network filter configuration to minimize the attack surface and prevent exploitation of similar memory management flaws.