CVE-2023-53559

A use-after-free flaw was found in the Linux kernel's ip_vti (IPsec Virtual Tunnel Interface) implementation when transmitting IPv6 packets with the SFB qdisc attached. A local user with CAP_NET_ADMIN capability can trigger this issue by configuring an ip_vti interface with an SFB qdisc and sending IPv6 traffic, causing the socket buffer control block to be modified during packet enqueuing and subsequently accessed after potential freeing during session decoding. This results in slab use-after-free, leading to kernel panic or potential memory corruption.

The ip_vti driver uses the socket buffer's control block (cb field) for internal state tracking. When the SFB (Stochastic Fair Blue) qdisc is attached to an ip_vti device, the qdisc modifies this cb field during packet enqueuing. Later, when decode_session6 is called on the transmit path, it attempts to access IP6CB(skb)->nhoff, which was designed only for the receive path and is not initialized during transmission. The modified cb field contents from the qdisc can cause the decoder to access invalid memory regions, potentially accessing already-freed slab objects.

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.