ICMP

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.

uRPF performs reverse routing lookup on every incoming packet’s source address — if the packet arrived on the wrong interface, it’s spoofed and dropped. When uRPF is disabled (the enterprise wireless default due to asymmetric routing), any host on the L2 segment can claim any source IP unconditionally. This is CWE-290 at Layer 3. Three confirmed attack classes in ArubaOS AOS-8: Smurf amplification (spoofed src → broadcast → victim flood), ICMP Timestamp leak (impersonate trusted management IP → elicit timestamp response), pre-auth reflection (use controller as intermediary). Single-packet pcap signature included. Linux sysctl and Cisco IOS uRPF configuration provided.

EtherLeak is an ICMP information disclosure class that resurfaces across vendors and decades — same root cause, different hardware. IP stacks that trust IP_Total_Length over actual frame length expose NIC DMA ring buffer contents via ICMP Echo. Combined with TTL=0, extraction runs at 1,800 bytes/second with zero IDS alerts, zero firewall logs. Covers full mechanism, threshold math, Suricata detection rules, and Scapy PoC.

Smurf amplification requires three weaknesses simultaneously: no uRPF allows IP source spoofing, directed broadcast forwarding delivers the packet to all VLAN hosts, hosts reply to broadcast ICMP Echo. RFC 2644 fixed router-level directed broadcast. L2 broadcast domains are unaffected — the packet never crosses a router. Enterprise wireless VLANs with 50-100 APs and controllers become 50-100x amplifiers. ICMP processing is pre-authentication: no credentials, no session. Two-machine verification: attacker sends spoofed src=victim to broadcast, victim captures unsolicited Echo Replies. pcap-level proof included.

Three compounding weaknesses in ArubaOS 8.13.2.0 ICMP handler: IP Total Length over-read reads 18 bytes past actual frame data into Ethernet padding (CWE-126); TTL=0 packets are processed and replied to in RFC 791 violation (CWE-1284); ICMP checksums are never validated (CWE-354). TTL=0 makes extraction invisible — routers don’t forward, IDS ignores, firewalls don’t log. 27/27 crafted probes confirmed. On physical AOS-8 hardware with active management traffic, the 18-byte DMA region contains previous frame fragments. CVE-2003-0001 and CVE-2021-3031 accepted on identical mechanism without physical hardware PoC.