{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-23450", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-01-13T15:37:46.020Z", "datePublished": "2026-04-03T15:15:33.144Z", "dateUpdated": "2026-04-03T15:15:33.144Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-04-03T15:15:33.144Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/smc: fix NULL dereference and UAF in smc_tcp_syn_recv_sock()\n\nSyzkaller reported a panic in smc_tcp_syn_recv_sock() [1].\n\nsmc_tcp_syn_recv_sock() is called in the TCP receive path\n(softirq) via icsk_af_ops->syn_recv_sock on the clcsock (TCP\nlistening socket). It reads sk_user_data to get the smc_sock\npointer. However, when the SMC listen socket is being closed\nconcurrently, smc_close_active() sets clcsock->sk_user_data\nto NULL under sk_callback_lock, and then the smc_sock itself\ncan be freed via sock_put() in smc_release().\n\nThis leads to two issues:\n\n1) NULL pointer dereference: sk_user_data is NULL when\n accessed.\n2) Use-after-free: sk_user_data is read as non-NULL, but the\n smc_sock is freed before its fields (e.g., queued_smc_hs,\n ori_af_ops) are accessed.\n\nThe race window looks like this (the syzkaller crash [1]\ntriggers via the SYN cookie path: tcp_get_cookie_sock() ->\nsmc_tcp_syn_recv_sock(), but the normal tcp_check_req() path\nhas the same race):\n\n CPU A (softirq) CPU B (process ctx)\n\n tcp_v4_rcv()\n TCP_NEW_SYN_RECV:\n sk = req->rsk_listener\n sock_hold(sk)\n /* No lock on listener */\n smc_close_active():\n write_lock_bh(cb_lock)\n sk_user_data = NULL\n write_unlock_bh(cb_lock)\n ...\n smc_clcsock_release()\n sock_put(smc->sk) x2\n -> smc_sock freed!\n tcp_check_req()\n smc_tcp_syn_recv_sock():\n smc = user_data(sk)\n -> NULL or dangling\n smc->queued_smc_hs\n -> crash!\n\nNote that the clcsock and smc_sock are two independent objects\nwith separate refcounts. TCP stack holds a reference on the\nclcsock, which keeps it alive, but this does NOT prevent the\nsmc_sock from being freed.\n\nFix this by using RCU and refcount_inc_not_zero() to safely\naccess smc_sock. Since smc_tcp_syn_recv_sock() is called in\nthe TCP three-way handshake path, taking read_lock_bh on\nsk_callback_lock is too heavy and would not survive a SYN\nflood attack. Using rcu_read_lock() is much more lightweight.\n\n- Set SOCK_RCU_FREE on the SMC listen socket so that\n smc_sock freeing is deferred until after the RCU grace\n period. This guarantees the memory is still valid when\n accessed inside rcu_read_lock().\n- Use rcu_read_lock() to protect reading sk_user_data.\n- Use refcount_inc_not_zero(&smc->sk.sk_refcnt) to pin the\n smc_sock. If the refcount has already reached zero (close\n path completed), it returns false and we bail out safely.\n\nNote: smc_hs_congested() has a similar lockless read of\nsk_user_data without rcu_read_lock(), but it only checks for\nNULL and accesses the global smc_hs_wq, never dereferencing\nany smc_sock field, so it is not affected.\n\nReproducer was verified with mdelay injection and smc_run,\nthe issue no longer occurs with this patch applied.\n\n[1] https://syzkaller.appspot.com/bug?extid=827ae2bfb3a3529333e9"}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["net/smc/af_smc.c", "net/smc/smc.h", "net/smc/smc_close.c"], "versions": [{"version": "8270d9c21041470f58348248b9d9dcf3bf79592e", "lessThan": "1e4f873879e075bbd4eb1c644d6933303ac5eba4", "status": "affected", "versionType": "git"}, {"version": "8270d9c21041470f58348248b9d9dcf3bf79592e", "lessThan": "f00fc26c8a06442b225a350fe000c0a11483e6a3", "status": "affected", "versionType": "git"}, {"version": "8270d9c21041470f58348248b9d9dcf3bf79592e", "lessThan": "cadf3da46c15523fba90d80c9955f536ee3b4023", "status": "affected", "versionType": "git"}, {"version": "8270d9c21041470f58348248b9d9dcf3bf79592e", "lessThan": "fd7579f0a2c84ba8a7d4f206201b50dc8ddf90c2", "status": "affected", "versionType": "git"}, {"version": "8270d9c21041470f58348248b9d9dcf3bf79592e", "lessThan": "1fab5ece76fb42a761178dcd0ebcbf578377b0dd", "status": "affected", "versionType": "git"}, {"version": "8270d9c21041470f58348248b9d9dcf3bf79592e", "lessThan": "6d5e4538364b9ceb1ac2941a4deb86650afb3538", "status": "affected", "versionType": "git"}, {"version": "ebfee3e153f67c8b38eb94a7062ee94aa6f92708", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["net/smc/af_smc.c", "net/smc/smc.h", "net/smc/smc_close.c"], "versions": [{"version": "5.18", "status": "affected"}, {"version": "0", "lessThan": "5.18", "status": "unaffected", "versionType": "semver"}, {"version": "6.1.167", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.130", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.78", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.20", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.19.10", "lessThanOrEqual": "6.19.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.0-rc5", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.18", "versionEndExcluding": "6.1.167"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.18", "versionEndExcluding": "6.6.130"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.18", "versionEndExcluding": "6.12.78"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.18", "versionEndExcluding": "6.18.20"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.18", "versionEndExcluding": "6.19.10"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.18", "versionEndExcluding": "7.0-rc5"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15.174"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/1e4f873879e075bbd4eb1c644d6933303ac5eba4"}, {"url": "https://git.kernel.org/stable/c/f00fc26c8a06442b225a350fe000c0a11483e6a3"}, {"url": "https://git.kernel.org/stable/c/cadf3da46c15523fba90d80c9955f536ee3b4023"}, {"url": "https://git.kernel.org/stable/c/fd7579f0a2c84ba8a7d4f206201b50dc8ddf90c2"}, {"url": "https://git.kernel.org/stable/c/1fab5ece76fb42a761178dcd0ebcbf578377b0dd"}, {"url": "https://git.kernel.org/stable/c/6d5e4538364b9ceb1ac2941a4deb86650afb3538"}], "title": "net/smc: fix NULL dereference and UAF in smc_tcp_syn_recv_sock()", "x_generator": {"engine": "bippy-1.2.0"}}}}

{}

{"cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/smc: fix NULL dereference and UAF in smc_tcp_syn_recv_sock()\n\nSyzkaller reported a panic in smc_tcp_syn_recv_sock() [1].\n\nsmc_tcp_syn_recv_sock() is called in the TCP receive path\n(softirq) via icsk_af_ops->syn_recv_sock on the clcsock (TCP\nlistening socket). It reads sk_user_data to get the smc_sock\npointer. However, when the SMC listen socket is being closed\nconcurrently, smc_close_active() sets clcsock->sk_user_data\nto NULL under sk_callback_lock, and then the smc_sock itself\ncan be freed via sock_put() in smc_release().\n\nThis leads to two issues:\n\n1) NULL pointer dereference: sk_user_data is NULL when\n accessed.\n2) Use-after-free: sk_user_data is read as non-NULL, but the\n smc_sock is freed before its fields (e.g., queued_smc_hs,\n ori_af_ops) are accessed.\n\nThe race window looks like this (the syzkaller crash [1]\ntriggers via the SYN cookie path: tcp_get_cookie_sock() ->\nsmc_tcp_syn_recv_sock(), but the normal tcp_check_req() path\nhas the same race):\n\n CPU A (softirq) CPU B (process ctx)\n\n tcp_v4_rcv()\n TCP_NEW_SYN_RECV:\n sk = req->rsk_listener\n sock_hold(sk)\n /* No lock on listener */\n smc_close_active():\n write_lock_bh(cb_lock)\n sk_user_data = NULL\n write_unlock_bh(cb_lock)\n ...\n smc_clcsock_release()\n sock_put(smc->sk) x2\n -> smc_sock freed!\n tcp_check_req()\n smc_tcp_syn_recv_sock():\n smc = user_data(sk)\n -> NULL or dangling\n smc->queued_smc_hs\n -> crash!\n\nNote that the clcsock and smc_sock are two independent objects\nwith separate refcounts. TCP stack holds a reference on the\nclcsock, which keeps it alive, but this does NOT prevent the\nsmc_sock from being freed.\n\nFix this by using RCU and refcount_inc_not_zero() to safely\naccess smc_sock. Since smc_tcp_syn_recv_sock() is called in\nthe TCP three-way handshake path, taking read_lock_bh on\nsk_callback_lock is too heavy and would not survive a SYN\nflood attack. Using rcu_read_lock() is much more lightweight.\n\n- Set SOCK_RCU_FREE on the SMC listen socket so that\n smc_sock freeing is deferred until after the RCU grace\n period. This guarantees the memory is still valid when\n accessed inside rcu_read_lock().\n- Use rcu_read_lock() to protect reading sk_user_data.\n- Use refcount_inc_not_zero(&smc->sk.sk_refcnt) to pin the\n smc_sock. If the refcount has already reached zero (close\n path completed), it returns false and we bail out safely.\n\nNote: smc_hs_congested() has a similar lockless read of\nsk_user_data without rcu_read_lock(), but it only checks for\nNULL and accesses the global smc_hs_wq, never dereferencing\nany smc_sock field, so it is not affected.\n\nReproducer was verified with mdelay injection and smc_run,\nthe issue no longer occurs with this patch applied.\n\n[1] https://syzkaller.appspot.com/bug?extid=827ae2bfb3a3529333e9"}], "id": "CVE-2026-23450", "lastModified": "2026-04-03T16:16:31.243", "metrics": {}, "published": "2026-04-03T16:16:31.243", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/1e4f873879e075bbd4eb1c644d6933303ac5eba4"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/1fab5ece76fb42a761178dcd0ebcbf578377b0dd"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/6d5e4538364b9ceb1ac2941a4deb86650afb3538"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/cadf3da46c15523fba90d80c9955f536ee3b4023"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/f00fc26c8a06442b225a350fe000c0a11483e6a3"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/fd7579f0a2c84ba8a7d4f206201b50dc8ddf90c2"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Received"}

{}

{}