CVE-2022-45934: Linux Kernel L2CAP Integer Wraparound Vulnerability - Exploit Analysis and Mitigation

A newly discovered vulnerability in the Linux kernel, identified as CVE-2022-45934, poses a significant risk to systems running Linux kernel versions up to and including 6..10. The issue resides in the l2cap_config_req function in the net/bluetooth/l2cap_core.c file, and involves an integer wraparound when processing L2CAP_CONF_REQ packets. Before diving into the details of the vulnerability, let's take a closer look at what L2CAP is and how it works.

L2CAP (Logical Link Control and Adaptation Protocol) is a protocol that provides a reliable and configurable communication channel for Bluetooth devices. It exists in the lower layers of the Bluetooth stack and is fundamental to managing connections between Bluetooth devices. As such, any vulnerability in this critical component has the potential to have wide-ranging impacts.

The Vulnerability

In the l2cap_config_req() function present in the l2cap_core.c file, an integer wraparound occurs as a result of mishandling large values while processing L2CAP config request (L2CAP_CONF_REQ) packets. This vulnerability can potentially allow an attacker to send malicious L2CAP_CONF_REQ packets, which can lead to a remotely exploitable condition resulting from an out-of-bounds read/write vulnerability.

Here is the relevant code snippet from the l2cap_core.c file

static void l2cap_config_req(struct l2cap_chan *chan,
                              struct l2cap_cmd_hdr *cmd, u16 cmd_len,
                              void *data)
{
   ...
   while (opt_len < cmd_len) {
      ...
      switch (opt[]) {
      case L2CAP_CONF_MTU:
         ...
         break;
      ...
   }
   ...
}

The vulnerability resides within the loop initiated through while (opt_len < cmd_len). When processing the L2CAP_CONF_REQ packet, the loop iterates through its options, with the opt_len variable incremented accordingly. If an attacker crafts a packet such that opt_len wraps around to a smaller value, the loop condition is still satisfied, leading to an out-of-bounds read/write access.

Exploit Details

To exploit this vulnerability, an attacker would need to send a sequence of malicious L2CAP_CONF_REQ packets to the targeted device. By carefully crafting these packets, the attacker could exploit the integer wraparound vulnerability, causing an out-of-bounds read/write access on the target system. As a result, the attacker could potentially:

Mitigations

To protect against this vulnerability, users are urged to either apply patches provided by their Linux distribution or upgrade their Linux kernel to version 6..11 or later. Maintainers of affected Linux distributions have already released patches addressing CVE-2022-45934, and users should ensure that their systems are updated accordingly.

In addition, organizations should take the necessary precautions to ensure that their Bluetooth devices are securely configured, with strong authentication mechanisms in place, and should consistently monitor for new vulnerabilities within their environment.

References

1. Official CVE-2022-45934 Details
2. Linux Kernel Git Repository
3. L2CAP Specification

Conclusion

CVE-2022-45934 is a critical security vulnerability affecting the Linux kernel up to and including version 6..10. It involves an integer wraparound in the l2cap_config_req function that potentially allows remote attackers to exploit affected systems by sending malicious L2CAP_CONF_REQ packets. To protect against this vulnerability, users are advised to upgrade their Linux kernel or apply the appropriate patches provided by their Linux distribution. Additionally, following security best practices in maintaining and configuring Bluetooth devices will help reduce the overall risk associated with this type of vulnerability.

Timeline

Published on: 11/27/2022 04:15:00 UTC
Last modified on: 04/11/2023 18:15:00 UTC