Linux Kernel TCP Timestamp Offset Vulnerability Reintroduction

A vulnerability in the Linux kernel's TCP implementation has been addressed by restoring the use of source ports in timestamp offset randomization. This change mitigates an off-path TCP source port leakage issue reported by Zhouyan Deng, which exploited a SYN cookie side-channel. The vulnerability was introduced by a previous modification that downgraded timestamp offset handling to be per-host, rather than per-port, allowing for potential port leakage. The issue affects the Linux kernel stable tree.

Impact

The restoration of per-port timestamp offset randomization helps prevent off-path attackers from leaking TCP source ports through a side-channel exploit, thereby enhancing the security of TCP connections.