OpenVPN/openvpn

OpenVPN 2.7.4 Windows 11 fails TLS negotiation while 2.6.17 works

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#1,036 opened on 2026/05/18

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説明

OpenVPN 2.7.4 on Windows 11 fails TLS negotiation with an existing legacy UDP setup that works correctly on:

  • Linux OpenVPN 2.6.14
  • Windows OpenVPN 2.6.17

Environment:

  • Windows 11 build 10.0.26200
  • OpenVPN 2.7.4
  • OpenSSL 3.6.2

Symptoms:

  • Client hangs at: TLS key negotiation failed to occur within 60 seconds
  • Server never logs: TLS: Initial packet from
  • tcpdump on intermediate pfSense shows repeated: UDP, length 14
  • No valid TLS handshake packets observed.

Same exact .ovpn config and certificates connect immediately with OpenVPN 2.6.17 on Windows and 2.6.14 on Linux.

Workaround: Downgrading Windows client from 2.7.4 to 2.6.17 resolves the issue instantly without configuration changes.

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