Network-Fingerprinting

The Windows registry key EnableICMPTimestampRep=0 is silently ignored by tcpip.sys — Ipv4pHandleTimestampRequest generates ICMP Type 14 replies unconditionally regardless of the registry value. Ghidra static analysis of tcpip.sys 10.0.26100.8457 reveals a second RFC 792 violation: Receive and Transmit timestamps are written in little-endian byte order while the adjacent IP Timestamp Option handler correctly calls htonl() on the same value. Confirmed via pcap, netstat ICMP counters, and WinDbg kernel breakpoints. CVE-1999-0524 scope analysis and WFP mitigation rule included.

icmp_timestamp() is implemented in every Linux kernel but never scrutinized at source level. A depth-8 ftrace investigation reveals six RFC 792 deviations: silent payload length threshold, Code field never validated, ts_ori echoed unconditionally across the full 32-bit range, conntrack state creation on Type 13, netfilter hook ordering, and reply generation path that bypasses standard socket accounting. Full call chain mapped: ip_rcv() → icmp_rcv() → icmp_timestamp() → icmp_reply() with all branching conditions documented.