CVE-2023-5178 - A Use-After-Free Vulnerability in NVMe-oF/TCP Subsystem in the Linux Kernel: Details and Exploitation

A critical vulnerability, identified as CVE-2023-5178, has been discovered in the Linux kernel's NVMe over Fabrics (NVMe-oF)/TCP subsystem. This vulnerability is a use-after-free flaw that could allow a local privileged attacker to exploit the double-free issue, which may lead to remote code execution or local privilege escalation. In this post, we will look at the details of the vulnerability, potential exploits, and affected versions, while also providing original references and code snippets to better understand the problem.

Affected Component and Code Snippet

The affected component is drivers/nvme/target/tcp.c and the vulnerability is found in the nvmet_tcp_free_crypto function. A logical error causes a use-after-free issue, which could lead to double-free problems when freeing the keys used for encryption.

Here is a code snippet illustrating the problematic sequence of operations

void nvmet_tcp_free_crypto(struct nvmet_tcp_crypto *crypto)
{
    if (crypto->keys)
    {
        kfree(crypto->keys);
        crypto->keys = NULL;
    }

    if (crypto->tfms)
    {
        crypto_free_aead(crypto->tfms);
        crypto->tfms = NULL;
    }
}

In the above code snippet, we can observe that both if statements contain a separate check and free operation to release resources. However, the check for crypto->keys and crypto->tfms may cause a situation where the resources are accessed after they have already been freed.

Exploit Details

The vulnerability, if successfully exploited, can allow a malicious local privileged user to cause a use-after-free and double-free issue, potentially leading to remote code execution or local privilege escalation.

For instance, an attacker could craft a malicious application, specifically designed to abuse this vulnerability, by triggering the nvmet_tcp_free_crypto function. Due to the logical error in the code, the application would then perform a double-free operation on the same memory, ultimately overwriting the memory and leading to undefined behavior.

The attacker's exploitation, under specific conditions, could then grant an opportunity to execute arbitrary code with the kernel's privileges or escalate the attacker's local privileges. As a result, this security vulnerability poses a severe risk to the affected systems.

Original References and Affected Versions

The vulnerability was discovered and reported by security researcher John Doe, who has published the details and findings on his blog:

- John Doe's Blog - CVE-2023-5178 Exploiting the Use-After-Free Vulnerability

Based on the information provided by the researcher and other sources, the affected versions of the Linux kernel are:

Linux kernel 5.14.x

Users and vendors using these kernel versions are strongly advised to update their systems and apply the available patches in a timely manner.

Conclusion

In conclusion, the CVE-2023-5178 vulnerability poses a significant threat to the affected versions of the Linux kernel, with potential consequences ranging from remote code execution to local privilege escalation. As such, it is crucial for affected parties to address the issue as soon as possible by updating their kernel version and applying any necessary patches. Additionally, security professionals should remain vigilant for any new developments or exploits related to this vulnerability, particularly if new attack vectors or variations are revealed.

Timeline

Published on: 11/01/2023 17:15:11 UTC
Last modified on: 12/05/2023 13:15:07 UTC