In recent times, security researchers have identified numerous vulnerabilities in various software systems. One such vulnerability, dubbed CVE-2023-4569, was discovered in the Linux Kernel, specifically in the nft_set_catchall_flush function located in net/netfilter/nf_tables_api.c. This memory leak flaw has the potential to allow local attackers to carry out a double-deactivation of catchall elements, leading to memory leakage. This article dives deeper into the details of the security flaw, its implications, and how it can be exploited. We also provide relevant code snippets and links to original references.

Description of the Flaw and Exploit Details

The Linux Kernel is the core component of any Linux-based operating system, providing crucial functionality in managing system resources, such as memory, CPU, and input/output devices. The net/netfilter/nf_tables_api.c file is an integral part of the Linux Kernel, housing the implementation of the netfilter framework responsible for packet filtering, network address translation, and port translation.

The discovered vulnerability, CVE-2023-4569, is classified as a memory leak flaw that exists within the nft_set_catchall_flush function. Memory leaks typically occur when memory resources allocated by a program are not freed or released after use. When this happens repeatedly over time, the program will consume an increasing amount of memory, ultimately exhausting the system's available memory resources.

The vulnerability potentially allows a local attacker to trigger a double-deactivation of catchall elements in a set. When this occurs, the memory allocated for these catchall elements is not freed, leading to a memory leak.

The following code snippet illustrates the vulnerable part of the nft_set_catchall_flush function

static void nft_set_catchall_flush(struct nft_set *set)
	struct nft_set_catchall *priv = nft_set_priv(set);
	struct nft_set_elem *elems[2];
	u32 cnt = ;

	if (nft_set_catchall_active(&priv->d))
		elems[cnt++] = &priv->d;
	if (nft_set_catchall_active(&priv->a))
		elems[cnt++] = &priv->a;

As seen in the code snippet, the function nft_set_catchall_flush iterates through catchall elements and checks if they are active. However, it does not handle the case where catchall elements have been doubly deactivated, resulting in the memory leak.


The impact of CVE-2023-4569, if exploited successfully, is significant as it can lead to the exhaustion of a system's available memory resources, causing the system to slow down or become unresponsive. Furthermore, while the vulnerability can only be exploited by local attackers, it holds the potential to compromise the security posture of Linux-based systems.

Mitigation and Recommendations

As of now, there has not been an official patch released for the CVE-2023-4569 vulnerability. However, users are advised to keep track of updates and patches for their Linux Kernel, as they may include essential security fixes. Additionally, users must restrict access to privileged system resources, as this can limit the potential for this vulnerability to be exploited.

Original References and Resources

1. The official CVE entry for CVE-2023-4569:
2. The Linux Kernel source file with the flawed function (net/netfilter/nf_tables_api.c):


CVE-2023-4569 is a significant vulnerability with the potential to compromise the integrity and performance of any Linux-based system. It is crucial for users and administrators to remain vigilant in safeguarding their systems, and to stay up-to-date with the latest security updates and patches to prevent potential exploits.


Published on: 08/28/2023 22:15:00 UTC
Last modified on: 09/10/2023 12:16:00 UTC