High [CVE-2026-63979] hand off the pinned file reference to accept_doit
This high-severity Red Hat Linux advisory covers CVE-2026-63979 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat package: kernel-rt.
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Summary
In the Linux kernel, the following vulnerability has been resolved: net/handshake: hand off the pinned file reference to accept_doit handshake_req_next() removes the request from the per-net pending list and drops hn_lock before handshake_nl_accept_doit() reads req->hr_sk->sk_socket and dereferences sock->file (once in FD_PREPARE() and again in get_file()).
In that window a consumer running tls_handshake_cancel() followed by sockfd_put() (svc_sock_free) or __fput_sync() (xs_reset_transport) releases sock->file. sock_release() then runs sock_orphan(), zeroing sk_socket, and frees the struct socket. The accept-side code either reads NULL through sk_socket or chases freed memory.
The submit-side sock_hold() does not prevent this. sk_refcnt protects struct sock, but struct socket and sock->file are independently refcounted via the file descriptor the consumer owns. Pinning sk leaves sock and sock->file unprotected.
Retarget the accept-side dereferences at req->hr_file, which was pinned at submit time, instead of req->hr_sk->sk_socket->file.
Pinning on its own is not sufficient: a consumer that cancels between handshake_req_next() returning and accept_doit reaching FD_PREPARE() takes the!remove_pending() branch in handshake_req_cancel() and drops hr_file before the accept side takes its own reference.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · medium-confidence parse· fetched 6 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · medium-confidence parse· fetched 6 days ago·verify at source
Mitigation
The source record does not include mitigation steps. That is not a statement that no fix exists — read the vendor advisory below for the authoritative guidance.
Official advisory · medium-confidence parse· fetched 6 days ago·verify at source
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