cbcvebase.
CVE-2026-23450
published 2026-04-03

CVE-2026-23450: In the Linux kernel, the following vulnerability has been resolved: net/smc: fix NULL dereference and UAF in smc_tcp_syn_recv_sock() Syzkaller reported a panic…

PriorityP352critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
EPSS
0.56%
42.8th percentile
In the Linux kernel, the following vulnerability has been resolved: net/smc: fix NULL dereference and UAF in smc_tcp_syn_recv_sock() Syzkaller reported a panic in smc_tcp_syn_recv_sock() [1]. smc_tcp_syn_recv_sock() is called in the TCP receive path (softirq) via icsk_af_ops->syn_recv_sock on the clcsock (TCP listening socket). It reads sk_user_data to get the smc_sock pointer. However, when the SMC listen socket is being closed concurrently, smc_close_active() sets clcsock->sk_user_data to NULL under sk_callback_lock, and then the smc_sock itself can be freed via sock_put() in smc_release(). This leads to two issues: 1) NULL pointer dereference: sk_user_data is NULL when accessed. 2) Use-after-free: sk_user_data is read as non-NULL, but the smc_sock is freed before its fields (e.g., queued_smc_hs, ori_af_ops) are accessed. The race window looks like this (the syzkaller crash [1] triggers via the SYN cookie path: tcp_get_cookie_sock() -> smc_tcp_syn_recv_sock(), but the normal tcp_check_req() path has the same race): CPU A (softirq) CPU B (process ctx) tcp_v4_rcv() TCP_NEW_SYN_RECV: sk = req->rsk_listener sock_hold(sk) /* No lock on listener */ smc_close_active(): write_lock_bh(cb_lock) sk_user_data = NULL write_unlock_bh(cb_lock) ... smc_clcsock_release() sock_put(smc->sk) x2 -> smc_sock freed! tcp_check_req() smc_tcp_syn_recv_sock(): smc = user_data(sk) -> NULL or dangling smc->queued_smc_hs -> crash! Note that the clcsock and smc_sock are two independent objects with separate refcounts. TCP stack holds a reference on the clcsock, which keeps it alive, but this does NOT prevent the smc_sock from being freed. Fix this by using RCU and refcount_inc_not_zero() to safely access smc_sock. Since smc_tcp_syn_recv_sock() is called in the TCP three-way handshake path, taking read_lock_bh on sk_callback_lock is too heavy and would not survive a SYN flood attack. Using rcu_read_lock() is much more lightweight. - Set SOCK_RCU_FREE on the SMC listen socket so that s

Affected

67 ranges· showing 25
VendorProductVersion rangeFixed in
debianlinux< linux 6.19.10-1 (forky)linux 6.19.10-1 (forky)
linuxlinux
linuxlinux>= 5.15.174 < 5.15.2035.15.203
linuxlinux>= 8270d9c21041470f58348248b9d9dcf3bf79592e < 1e4f873879e075bbd4eb1c644d6933303ac5eba41e4f873879e075bbd4eb1c644d6933303ac5eba4
linuxlinux>= 8270d9c21041470f58348248b9d9dcf3bf79592e < f00fc26c8a06442b225a350fe000c0a11483e6a3f00fc26c8a06442b225a350fe000c0a11483e6a3
linuxlinux>= 8270d9c21041470f58348248b9d9dcf3bf79592e < cadf3da46c15523fba90d80c9955f536ee3b4023cadf3da46c15523fba90d80c9955f536ee3b4023
linuxlinux>= 8270d9c21041470f58348248b9d9dcf3bf79592e < fd7579f0a2c84ba8a7d4f206201b50dc8ddf90c2fd7579f0a2c84ba8a7d4f206201b50dc8ddf90c2
linuxlinux>= 8270d9c21041470f58348248b9d9dcf3bf79592e < 1fab5ece76fb42a761178dcd0ebcbf578377b0dd1fab5ece76fb42a761178dcd0ebcbf578377b0dd
linuxlinux>= 8270d9c21041470f58348248b9d9dcf3bf79592e < 6d5e4538364b9ceb1ac2941a4deb86650afb35386d5e4538364b9ceb1ac2941a4deb86650afb3538
linuxlinux>= ebfee3e153f67c8b38eb94a7062ee94aa6f92708 < f315277856caeafcd996c2611afc085ca2d53275f315277856caeafcd996c2611afc085ca2d53275
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel>= 0 < 6.19.10-16.19.10-1
linuxlinux_kernel>= 5.15.174 < 5.15.2035.15.203
linuxlinux_kernel>= 5.18 < 6.1.1676.1.167
linuxlinux_kernel>= 6.13 < 6.18.206.18.20
linuxlinux_kernel>= 6.19 < 6.19.106.19.10
linuxlinux_kernel>= 6.2 < 6.6.1306.6.130
linuxlinux_kernel>= 6.7 < 6.12.786.12.78
ubuntulinux
ubuntulinux-aws
ubuntulinux-aws-5.15

CVSS provenance

nvdv3.19.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
vendor_ubuntu8.8HIGH
vendor_redhat7.0HIGH
Stop checking back — get the weekly exploitation signal.

Every Monday: what got weaponized or added to CISA KEV in the last seven days — each CVE cross-linked to its PoC, Nuclei template, and detection rule. Free, one email a week, unsubscribe in one click.