Microsoft Confirms VPN Bug Caused by Windows Cumulative Update KB5009543

Microsoft has recently acknowledged a VPN bug caused by the updates it launched as part of this month’s Patch Tuesday cycle, including KB5009543. The company explains on the Windows Health Dashboard page that devices with IPSEC connections configured to use a vendor ID might be unable to connect to VPN. The culprit is the most recent set of Windows cumulative updates, with the software giant explaining that all Windows 10 versions, as well as Windows 11, are currently affected. “After installing KB5009543, 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,” the company said. The workaround and the full fix At this point, however, Microsoft says it’s still investigating the problem, and it expects ...