Critical severity · published Jul 19, 2026
CVE-2026-63979
net/handshake: hand off the pinned file reference to accept_doit
9.8
CVSS
0.6%
EPSS
No
On KEV
Description
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. Hand off an additional file reference
inside handshake_req_next(), under hn_lock, so the accept side
operates on a reference that no concurrent handshake_req_cancel()
can revoke. FD_PREPARE() consumes that handed-off reference,
either by transferring it to the new fd in fd_publish() or by
dropping it in the cleanup destructor on error; the explicit
get_file() that previously balanced FD_PREPARE() is therefore
redundant and goes away.
Update handshake_req_cancel_test2 and _test3 to simulate the
FD_PREPARE() consumption with an fput() so the kunit file-count
assertions stay balanced.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.6% · higher than 50% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
LI
Linux · Linux
3b3009ea8abb713b022d94fba95ec270cf6e7eae before b869e3e4ce1996df23b3efdbbe9a64c4ab81d745; 3b3009ea8abb713b022d94fba95ec270cf6e7eae before 2f28dbb30b88eafab8d49aaec94710b4e12dea8e; 3b3009ea8abb713b022d94fba95ec270cf6e7eae before 68eba6519cbd6359fb554a9720f3a3b6b2eba23f; 3b3009ea8abb713b022d94fba95ec270cf6e7eae before c06876d4fac38f35820946ee3b1be7d7da799cd4; 3b3009ea8abb713b022d94fba95ec270cf6e7eae before f4251190e58b209999c1ba9e6d2976136a1be055; 6.4 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-63979
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-63979
git.kernel.org
https://git.kernel.org/stable/c/2f28dbb30b88eafab8d49aaec94710b4e12dea8e
git.kernel.org
https://git.kernel.org/stable/c/68eba6519cbd6359fb554a9720f3a3b6b2eba23f
git.kernel.org
https://git.kernel.org/stable/c/b869e3e4ce1996df23b3efdbbe9a64c4ab81d745
git.kernel.org
https://git.kernel.org/stable/c/c06876d4fac38f35820946ee3b1be7d7da799cd4
git.kernel.org
https://git.kernel.org/stable/c/f4251190e58b209999c1ba9e6d2976136a1be055
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