CVE-2023-53338: Linux Kernel

High severity, CVSS 7.8. EPSS: 0.6% chance of exploitation in the next 30 days.

In the Linux kernel, the following vulnerability has been resolved: lwt: Fix return values of BPF xmit ops BPF encap ops can return different types of positive values, such like NET_RX_DROP, NET_XMIT_CN, NETDEV_TX_BUSY, and so on, from function skb_do_redirect and bpf_lwt_xmit_reroute. At the xmit hook, such return values would be treated implicitly as LWTUNNEL_XMIT_CONTINUE in ip(6)_finish_output2. When this happens, skbs that have been freed would continue to the neighbor subsystem, causing use-after-free bug and kernel crashes. To fix the incorrect behavior, skb_do_redirect return values can be simply discarded, the same as tc-egress behavior. On the other hand, bpf_lwt_xmit_reroute returns useful errors to local senders, e.g. PMTU information. Thus convert its return values to avoid the conflict with LWTUNNEL_XMIT_CONTINUE.

Affected products

• Linux Linux Kernel: from 4.10, before 5.4.257 (fixed in 5.4.257); from 5.5, before 5.10.195 (fixed in 5.10.195); from 5.11, before 5.15.132 (fixed in 5.15.132); from 5.16, before 6.1.53 (fixed in 6.1.53); from 6.2, before 6.4.16 (fixed in 6.4.16); from 6.5, before 6.5.3 (fixed in 6.5.3)

Published 2025-09-17. Last modified 2026-08-04.