CVE-2026-68398

A flaw was found in the Linux kernel's Point-to-Point Protocol (PPP) over L2TP (Layer 2 Tunneling Protocol) implementation. An unprivileged user can exploit a Use-After-Free (UAF) vulnerability, where the system attempts to use memory after it has been freed. This can lead to memory corruption, potentially allowing an attacker to cause system instability or execute arbitrary code.

This vulnerability is rated as an Important impact for Red Hat Enterprise Linux because an unprivileged local attacker can exploit this race condition during socket release to corrupt kernel memory, potentially resulting in local privilege escalation or a complete system crash. Although Layer 2 Tunneling Protocol (L2TP) over PPP is not commonly active by default, the underlying socket family remains accessible to non-root users on standard configurations. Consequently, unauthenticated remote exploitation is not possible, but local users can compromise system integrity without requiring administrative permissions.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

If PPP over L2TP functionality is not required, prevent the 'pppol2tp' kernel module from loading to mitigate this vulnerability. Create a file named /etc/modprobe.d/disable-pppol2tp.conf with the following content:

install pppol2tp /bin/true

After creating the file, regenerate the initramfs and reboot the system for the changes to take effect. This action may impact services relying on PPP over L2TP.