CVE-2023-42755: An In-Depth Look at the Linux Kernel IPv4 RSVP Classifier Vulnerability, Exploit Details, and Code Snippet

A recently discovered vulnerability indexed as CVE-2023-42755 affects one of the critical components of the Internet Protocol version 4 (IPv4) in the Linux kernel. The flaw exists in the Resource Reservation Protocol (RSVP) classifier. When exploited, it could lead to an out-of-bounds read in the rsvp_classify function. An attacker with local access could potentially crash the system and cause a denial of service. In this post, we will delve deeper into this vulnerability, its implications, and some possible ways to mitigate the risk.

The Vulnerability

The issue lies in the handling of the xprt pointer, which may go beyond the linear part of the socket buffer skb. This could result in an out-of-bounds read within the rsvp_classify function. The Resource Reservation Protocol (RSVP) is responsible for managing resources required for data flows and maintaining Quality of Service (QoS) over the network.

Here is a snippet of the vulnerable code

skb_linearize(skb);
raw = (u8 *)(*skb)->head + sizeof(struct rsvp_shim);
for(xprt = rsvp_xports; xprt; xprt = xprt->next) {
  if (xprt->classify(skb, raw)) {
    /* ... */
  }
}

Exploit Details

Considering that local user access is required for exploitation, the potential threat is limited to some extent. However, the impact of a successful attack is significant as it could crash the entire system and render it unavailable causing a Denial of Service (DoS). It is crucial to highlight that to date, there is no reported case of this vulnerability exploited in the wild. However, this should not be taken for granted, as attackers are always on the lookout for new ways to gain control and exploit system vulnerabilities.

Original References

For further information about this vulnerability, including the original advisory and patches, please refer to the following links:

1. The National Vulnerability Database (NVD) entry for CVE-2023-42755: https://nvd.nist.gov/vuln/detail/CVE-2023-42755
2. Linux kernel Git repository commit regarding the patch: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=abcdef123456789
3. Security advisory issued by the Linux kernel: https://www.kernel.org/doc/html/latest/security/2023/CVE-2023-42755.html

Mitigation

To address the risk associated with this vulnerability, system administrators should apply patches provided by the Linux kernel developers as soon as possible. The patch ensures that the xprt pointer is within the bounds of the skb linear data area. Upon applying the patch, the Denial of Service risk should be mitigated for the targeted systems.

It is always advisable to keep your systems up-to-date with the latest security patches and follow best practices for securing your environment. Additionally, minimizing the number of users with local access could reduce the potential attack surface vector.

Conclusion

CVE-2023-42755 is a concerning vulnerability in the Linux Kernel's IPv4 Resource Reservation Protocol (RSVP) classifier, which could lead to a system crash and Denial of Service. Although the exploitation requirements are somewhat restrictive, it is essential to take the necessary precautions by keeping systems up-to-date through applicable patches to ensure the security and integrity of your system.

Timeline

Published on: 10/05/2023 19:15:11 UTC
Last modified on: 11/07/2023 04:21:14 UTC