Patch Tuesdays are exciting because Microsoft fixes all those nagging minor issues and security problems that have popped up. However, sometimes things go sideways, which happened recently, as a Windows patch made some types of VPNs stop working.
After Microsoft released the latest round of updates for Patch Tuesday, IPSEC IKE and L2TP VPN connections were failing for many users. This was particularly problematic for businesses that relied on these connections for remote employees to access private systems.
Microsoft’s documentation broke down the problem: “After installing KB5009566, IP Security (IPSEC) connections which contain a Vendor ID might fail. VPN connections using Layer 2 Tunneling Protocol (L2TP) or IP security Internet Key Exchange (IPSEC IKE) might also be affected.”
Windows’ built-in VPN was most commonly affected, but some users reported issues with third-party VPN software that used IPSEC IKE and L2TP connections, as well.
Thankfully, the issue was resolved with an out-of-band update labeled KB5010795, which is available now for Windows 11, Windows 10, Windows Server 2022, Windows Server 2019, and Windows Server 2016. If you’re running into problems with your IPSEC IKE and L2TP VPN, make sure to update Windows to fix the problem.