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Event ID 4965: IPsec received a packet from a remote computer with an incorrect Security Parameter Index (SPI)

Windows Event ID Lookup: What Windows event IDs mean: 4625, 4624, 4740, 6008, 41, 7045, 1102 and 3,000 more, with Windows' own message text, the fields and what to check.

Look up a Windows event ID from Event Viewer, a SIEM alert or a log export: what it means, the fields it records, and what to check. Many IDs are used by more than one source (event 41 is both a Kernel-Power crash and a boot error), so every definition is shown, the one people usually mean first. The message text is Windows' own, read from the event providers of Windows 10.0.26200.0, 2026-10-28; the notes are ours, based on Microsoft's security auditing reference.

Try: 4625, 4624, 4740, 6008, 41, 1074, 7045, 1102, 4104, 1149

IPsec received a packet from a remote computer with an incorrect Security Parameter Index (SPI).

Event 4965
Security-Auditing
Security log
Audit
Message and fields (as Event Viewer shows them) 
IPsec received a packet from a remote computer with an incorrect Security Parameter Index (SPI). This is usually caused by malfunctioning hardware that is corrupting packets. If these errors persist, verify that the packets sent from the remote computer are the same as those received by this computer. This error might also indicate interoperability problems with other IPsec implementations. In that case, if connectivity is not impeded, then these events can be ignored.

Remote Network Address:	…
Inbound SA SPI:		…