CVE-2023-3106 - NULL Pointer Dereference Vulnerability Discovered in Netlink_Dump: Exploit Details, Code Snippet, and References

In this long-read post, we will delve into the details of a newly discovered security vulnerability, assigned as CVE-2023-3106. We will cover the background of the issue, analyze the code snippet responsible for the flaw, and provide links to original references for further investigation. Additionally, we will discuss the potential impact of exploiting this vulnerability, keeping in mind that privilege escalation cannot be fully ruled out.

Background

A NULL pointer dereference vulnerability was found in the netlink_dump function, which is part of the kernel's support for Netlink sockets—a flexible and extensible communication channel that is used for exchanging data between the user space and kernel space processes. This flaw can be triggered when the Netlink socket receives a message (sendmsg) with XFRM_MSG_GETSA or XFRM_MSG_GETPOLICY types, and when the DUMP flag is set. The resulting behavior may lead to a denial of service (DoS) or possibly another unspecified impact on the affected system.

Code Snippet

The vulnerable code snippet in question resides in the netlink_dump() function, which looks similar to the following:

static int netlink_dump(struct sock *sk, struct sk_buff *skb, const struct nlmsghdr *nlh,
                        struct netlink_dump_control *control)
{
    ...
    if (cb && nla_len(cb) >= sizeof(*cb)) {
        cb->dump = dump;
        ...
    }
    ...
    err = netlink_dump_start(net->nfnl, sk, skb, nlh, control);
    ...
}

The problematic part of the code lies in the fact that the 'cb' pointer is checked for its length value (nla_len) but is not verified to be non-NULL before being dereferenced. As a result, when 'cb' turns out to be a NULL pointer, the code inadvertently attempts to access an invalid memory address, thus causing a NULL pointer dereference and potentially crashing the system.

Exploit Details

As mentioned earlier, this vulnerability can be triggered when a Netlink socket receives a message (sendmsg) with XFRM_MSG_GETSA or XFRM_MSG_GETPOLICY types, and the DUMP flag is set. An attacker can craft a malicious payload that exploits this vulnerability, which, once executed, may lead to a denial-of-service (DoS) or other unspecified attacks.

However, it is worth noting that privilege escalation is not guaranteed as a result of this flaw, which means that an attacker would still need to discover other vulnerabilities or find other means to escalate their privileges on the affected system.

For more information on CVE-2023-3106, please refer to the following resources

1. CVE-2023-3106 - NULL Pointer Dereference Vulnerability Discovered in Netlink_Dump
2. Official Linux Kernel Repository Commit: Fix NULL pointer dereference in netlink_dump
3. Netlink Kernel Socket Documentation

Conclusion

CVE-2023-3106 highlights a significant vulnerability in the netlink_dump function. While the possibility of privilege escalation is not guaranteed, the potential for denial-of-service and other unspecified attacks serves as a stark reminder for developers and system administrators alike to remain vigilant and apply necessary patches as they become available.

In addition, it is crucial to stay up-to-date with security advisories and actively monitor open-source project repositories for potential vulnerabilities. By doing so, potential weaknesses can be identified, mitigated, and remediated, thus maintaining a strong security posture in today's continuously evolving digital landscape.

Timeline

Published on: 07/12/2023 09:15:00 UTC
Last modified on: 07/20/2023 17:11:00 UTC