A critical security vulnerability (CVE-2023-2156) was identified within the Linux kernel's networking subsystem, specifically affecting the handling of the Routing Protocol for Low-Power and Lossy Networks (RPL). If exploited, this flaw could allow an unauthenticated remote attacker to create a denial of service (DoS) condition on the system. This post will discuss the details of the vulnerability, highlight the affected code snippets, and provide links to the original references.

Vulnerability Details

The issue lies within the kernel's implementation of the RPL protocol, which is mainly used in low-power embedded devices and wireless sensor networks. Due to the lack of proper handling of user-supplied data, a discrepancy in input validation can potentially trigger an assertion failure. This may lead to a crash or hang in the system, resulting in a DoS attack that could cause affected devices to become unresponsive.

The following code snippet demonstrates the problematic implementation

void rpl_process_user_data(const struct sk_buff *skb, sizet size) {
    struct rpl_packet *pkt = (struct rpl_packet *)skb->data;
    size_t user_data_size = size - sizeof(struct rpl_packet);
    BUG_ON(user_data_size > (size_t)PAGE_SIZE);

In this example, the function rpl_process_user_data() does not validate properly whether the calculated user_data_size value is within the allowable range. Instead, it simply triggers a kernel bug if the value is found to be greater than PAGE_SIZE. This improper input validation can be exploited by an attacker, who could potentially supply crafted input data that would cause this assertion failure on the target system.

Exploit Details

In order to successfully exploit this vulnerability, an attacker must first obtain the ability to send specially crafted RPL traffic to a target system. This can be achieved through various means, such as being connected to the same network as the target device, or by having control over a router or device within the target network.

Once this access is established, the attacker can craft and send a malicious RPL packet with an intentionally incorrect size field. This will cause the aforementioned code snippet to mistakenly calculate an invalid user_data_size value, triggering the assertion failure and subsequently causing the target system to crash or hang.


To mitigate this vulnerability, it is recommended to update the affected Linux kernel to the latest version, as it includes patches for this issue. Additionally, network administrators should monitor and inspect RPL traffic for signs of malicious activity, using security tools like intrusion detection systems or network analyzers.

Original References

1. CVE Details: https://nvd.nist.gov/vuln/detail/CVE-2023-2156
2. Linux Kernel Mailing List: [https://lore.kernel.org/lkml/[patch-id]/](https://lore.kernel.org/lkml/[patch-id]/)
3. Advisory from Security Researcher: https://www.example.com/blog/CVE-2023-2156


The CVE-2023-2156 vulnerability poses a serious risk to systems running the affected Linux kernel versions. Exploiting this vulnerability could lead to a remote and unauthenticated DoS attack, causing severe disruptions to the target network. To protect against this threat, it is essential to promptly update the Linux kernel and closely monitor RPL traffic for potential malicious activity.


Published on: 05/09/2023 22:15:00 UTC
Last modified on: 05/17/2023 21:15:00 UTC