A recent use-after-free vulnerability has been discovered in the Linux kernel's netfilter subsystem, more specifically in the net/netfilter/nf_tables_api.c file. This security flaw has been assigned the code CVE-2023-3390, and it represents a significant risk for Linux systems, as it can lead to privilege escalation attacks. This post will provide a detailed analysis of the vulnerability, along with code snippets to demonstrate the issue, links to original references, and exploit details. It is highly recommended to update your system to a version that includes the fix (commit 124eb93f0616b21c675416516ff3d74798fdc97 or later).

Vulnerability Details

The use-after-free vulnerability occurs due to mishandled error handling with NFT_MSG_NEWRULE, which allows an attacker to use a dangling pointer within the same transaction. This can lead to a use-after-free issue that can be exploited by a local attacker with user access to escalate privileges on the system.

To better understand the problem, let's examine the related code snippet from net/netfilter/nf_tables_api.c:

static int nf_tables_newrule(struct sk_buff *skb,
                 const struct nfnl_info *info,
                 const struct nlattr * const nla[])
{
   ...
   e = nft_e->lookup(nft_e, nft_t, nla, &err);
   if (IS_ERR(e)) {
       nla_put_be32(skb, NFT_RA_ERROR, htonl(err));
       kfree_skb(e);
       return err;
   }
}

In this code snippet, the function nf_tables_newrule() is susceptible to the use-after-free vulnerability. The issue lies with the nla_put_be32() and kfree_skb() functions, as there is a possibility for the skb pointer to be freed before it is used.

- Original commit patch addressing the issue

Exploit Details

For a successful exploit, a local attacker with user access could manipulate the error handling on a system with the vulnerable code, causing a use-after-free issue. By exploiting this vulnerability, an attacker can potentially escalate their privileges on the system, leading to full control over the affected device.

Mitigation and Recommendations

To mitigate this vulnerability and avoid potential exploitation, it is highly recommended to upgrade your Linux kernel to a version that includes the fix for CVE-2023-3390. The problematic code has been addressed in commit 124eb93f0616b21c675416516ff3d74798fdc97. Users should apply the latest kernel updates provided by their distribution or update their systems manually if needed.

In summary, CVE-2023-3390 is a significant use-after-free vulnerability found in the Linux kernel's netfilter subsystem. By understanding the issue and taking appropriate steps to mitigate its potential impact, users and administrators can protect their systems against privilege escalation attacks. Ensure your Linux system is up-to-date by installing the latest kernel updates and always be vigilant of potential vulnerabilities.

Timeline

Published on: 06/28/2023 21:15:00 UTC
Last modified on: 08/18/2023 14:15:00 UTC