When using ECH, do not include the PSK extension in the outer hello. Including the PSK extension allows for a degradation in privacy, as an on-path attacker can harvest outer client hellos, and then construct new hellos using the PSK extension and arbitrary guessed SNI values, replaying them to the target server. If the server rejects the PSK, the handshake will continue, but if the PSK is accepted, the binder check will fail. Thanks to Coia Prant (github.com/rbqvq) for reporting this issue. Fixes CVE-2026-42505 Updates #79282 Fixes #80175 Change-Id: Ib3a3c948106a57c1b07b9e61a58cbf757848be18 Reviewed-on: https://go-review.googlesource.com/c/go/+/775960 Auto-Submit: Roland Shoemaker <roland@golang.org> TryBot-Bypass: Roland Shoemaker <roland@golang.org> Reviewed-by: Daniel McCarney <daniel@binaryparadox.net> Reviewed-by: Carlos Amedee <carlos@golang.org> (cherry picked from commit 137b806) Reviewed-on: https://go-review.googlesource.com/c/go/+/794921 TryBot-Bypass: Junyang Shao <shaojunyang@google.com> Reviewed-by: Junyang Shao <shaojunyang@google.com> Commit-Queue: Roland Shoemaker <roland@golang.org> Auto-Submit: Junyang Shao <shaojunyang@google.com> Commit-Queue: Junyang Shao <shaojunyang@google.com>

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crypto/tls: omit PSK in ECH outer client hello [1.26 backport] #80175

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