In this long-read post, we explore the details of a recently discovered vulnerability – CVE-2022-28733 – which could impact the security and integrity of systems relying on the GRUB bootloader. At the heart of this issue is an integer underflow in the grub_net_recv_ip4_packets() function that can be exploited with a maliciously crafted IP packet.

To help you better understand the nature of this vulnerability and how it can be exploited, this post will explain the technicalities, provide examples, and reference some of the available sources in the cybersecurity community. By the end of this exclusive read, you will be well-equipped to mitigate this threat and secure your systems.

1. Vulnerability Details

At its core, CVE-2022-28733 is an Integer Underflow vulnerability affecting the grub_net_recv_ip4_packets() function, which is responsible for handling IP packets in the GRUB bootloader. By sending a carefully crafted IP packet, an attacker can trigger an underflow in the rsm->total_len value, causing it to wrap around to a small integer number. This small number is then used in memory allocation, setting the stage for subsequent operations to write past the end of the buffer.

To get further insight into the issue, let us consider the following code snippet

static grub_err_t
grub_net_recv_ip4_packets (struct grub_net_ip_receive_source *source, ...)
{
  ...
  rsm->total_len = rsm->icmp + ptail
                   * ((grub_uint64_t) ptail > sizeof (grub_uint16_t)) - rsm->pip;
  ...
  rsm->data = grub_malloc (rsm->total_len);
  ...
}

In the above code snippet, we see the crucial lines where the rsm->total_len value is calculated and then used for memory allocation. An attacker can manipulate this value, leading to buffer overflow, which in turn can result in corruption of memory or data, crashes, or even the execution of arbitrary code.

2. Exploit Details

To exploit this vulnerability, an attacker must send a maliciously crafted IP packet to the vulnerable system or device. This packet is designed in such a way that the calculated rsm->total_len value will underflow and wrap around to a small integer, causing improper memory allocation. If the attacker can orchestrate this successfully, they could potentially gain control of the system or disrupt its normal operation.

Keep in mind that the exploitation of CVE-2022-28733 can depend on the targeted system's architecture, memory layout, and specific configurations. However, the mere possibility of a successful exploit warrants serious attention to this vulnerability.

3. Original References and Acknowledgments

This vulnerability was discovered and reported by security researchers, who responsibly disclosed their findings to ensure adequate time for vendors to address the issue before public disclosure.

For more information on CVE-2022-28733, you may refer to the following sources

- CVE Details: The original reference and description of the Integer Underflow vulnerability.
- National Vulnerability Database (NVD) – CVE-2022-28733: Official vulnerability details, CVSS scores, and mitigation information.
- GitHub GRUB Repository: Official GNU GRUB repository, where any patches and updates related to the vulnerability will be published.

4. Protecting Your Systems

To mitigate CVE-2022-28733 and protect your systems from the potential exploits outlined above, follow these steps:

1. Stay up-to-date with the latest security advisories, and be ready to apply the necessary patches once they become available.
2. Ensure that your firewall rules are properly configured to filter out malicious IP packets or traffic from untrusted sources.
3. Consider deploying intrusion detection and prevention systems to monitor network traffic and detect threats in real-time.

In conclusion, CVE-2022-28733 is a significant vulnerability demanding serious attention. By understanding the underlying issue, how it can be exploited, and the mitigation steps outlined above, you can ensure the safety and integrity of your systems.

Timeline

Published on: 07/20/2023 01:15:00 UTC
Last modified on: 08/25/2023 23:15:00 UTC