CVE-2023-3390: 
Linux Kernel vulnerability analysis and mitigation

A use-after-free vulnerability (CVE-2023-3390) was discovered in the Linux kernel's netfilter subsystem, specifically in net/netfilter/nftablesapi.c. The vulnerability stems from mishandled error handling with NFTMSGNEWRULE, which makes it possible to use a dangling pointer in the same transaction. This vulnerability was discovered in June 2023 and affects Linux kernel versions prior to 6.4-rc7 (Kernel Patch).

The vulnerability resides within the kernel's netfilter subsystem, which is responsible for packet filtering and network address translation. The flaw occurs when processing named and anonymous sets in batch requests, where a reference count within the nftparseregister function of the nftablesapi.c file is improperly handled. The issue has been assigned a CVSS v3.1 score of 7.8 (HIGH) with the vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H (NVD).

The vulnerability allows a local attacker with user access to cause a privilege escalation issue. When successfully exploited, it can lead to disclosure of sensitive information, addition or modification of data, or Denial of Service (DoS). The severity is particularly concerning as it affects the kernel level, potentially granting complete control over the affected machine (Security Online).

The primary mitigation is to upgrade past commit 1240eb93f0616b21c675416516ff3d74798fdc97. For systems that cannot be immediately updated, it is recommended to disable the ability for unprivileged users to create namespaces. This can be done temporarily using the command 'sysctl -w kernel.unprivilegedusernsclone=0' or permanently by adding 'kernel.unprivilegedusernsclone=0' to /etc/sysctl.d/99-disable-unpriv-userns.conf (Ubuntu Security).