Vulnerability record · CVE-2025-68775 · published 13 January 2026
CVE-2025-68775: In the Linux kernel, the following vulnerability has been resolved: net/handshake: duplicate handshake cancel…
In the Linux kernel, the following vulnerability has been resolved: net/handshake: duplicate handshake cancellations leak socket When a handshake request is cancelled it is removed from the handshake_net->hn_requests list, but it is still present in the handshake_rhashtbl until it is destroyed. If a second cancellation request arrives for the same handshake request, then remove_pending() will return false... and assuming HANDSHAKE_F_REQ_COMPLETED isn't set in req->hr_flags, we'll continue processing through the out_true label, where we put another reference on the sock and a refcount underflow occurs. This can happen for example if a handshake times out - particularly if the SUNRPC client sends the AUTH_TLS probe to the server but doesn't follow it up with the ClientHello due to a problem with tlshd. When the timeout is hit on the server, the server will send a FIN, which triggers a cancellation request via xs_reset_transport(). When the timeout is hit on the client, another cancellation request happens via xs_tls_handshake_sync(). Add a test_and_set_bit(HANDSHAKE_F_REQ_COMPLETED) in the pending cancel path so duplicate cancels can be detected.
Description
In the Linux kernel, the following vulnerability has been resolved: net/handshake: duplicate handshake cancellations leak socket When a handshake request is cancelled it is removed from the handshake_net->hn_requests list, but it is still present in the handshake_rhashtbl until it is destroyed. If a second cancellation request arrives for the same handshake request, then remove_pending() will return false... and assuming HANDSHAKE_F_REQ_COMPLETED isn't set in req->hr_flags, we'll continue processing through the out_true label, where we put another reference on the sock and a refcount underflow occurs. This can happen for example if a handshake times out - particularly if the SUNRPC client sends the AUTH_TLS probe to the server but doesn't follow it up with the ClientHello due to a problem with tlshd. When the timeout is hit on the server, the server will send a FIN, which triggers a cancellation request via xs_reset_transport(). When the timeout is hit on the client, another cancellation request happens via xs_tls_handshake_sync(). Add a test_and_set_bit(HANDSHAKE_F_REQ_COMPLETED) in the pending cancel path so duplicate cancels can be detected.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
References
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Source: NIST National Vulnerability Database (record CVE-2025-68775), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.
