CVE-2023-1829

Published: 12 April 2023

A use-after-free vulnerability in the Linux Kernel traffic control index filter (tcindex) can be exploited to achieve local privilege escalation. The tcindex_delete function which does not properly deactivate filters in case of a perfect hashes while deleting the underlying structure which can later lead to double freeing the structure. A local attacker user can use this vulnerability to elevate its privileges to root. We recommend upgrading past commit 8c710f75256bb3cf05ac7b1672c82b92c43f3d28.

From the Ubuntu Security Team

It was discovered that the Traffic-Control Index (TCINDEX) implementation in the Linux kernel did not properly perform filter deactivation in some situations. A local attacker could possibly use this to gain elevated privileges. Please note that with the fix for this CVE, kernel support for the TCINDEX classifier has been removed.

Mitigation

Block autoloading the cls_tcindex module by adding the following
lines to /etc/modprobe.d/blacklist-tcindex.conf:
  blacklist cls_tcindex

Status