{"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": "2026-05-11T22:07:13.634Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-05-11T22:07:13.634Z"}, "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"}], "metrics": [{"cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL"}}], "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": "ebfee3e153f67c8b38eb94a7062ee94aa6f92708", "lessThan": "f315277856caeafcd996c2611afc085ca2d53275", "status": "affected", "versionType": "git"}, {"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"}]}, {"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": "5.15.203", "lessThanOrEqual": "5.15.*", "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", "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": "5.15.174", "versionEndExcluding": "5.15.203"}, {"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"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/f315277856caeafcd996c2611afc085ca2d53275"}, {"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": "2026-04-27T14:16:33.563", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 9.8, "baseSeverity": "CRITICAL", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 5.9, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}]}, "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/f315277856caeafcd996c2611afc085ca2d53275"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/fd7579f0a2c84ba8a7d4f206201b50dc8ddf90c2"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Awaiting Analysis"}

{"bugzilla": {"description": "kernel: net/smc: fix NULL dereference and UAF in smc_tcp_syn_recv_sock()", "id": "2454799", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2454799"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.0", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H", "status": "draft"}, "cwe": "CWE-476", "details": ["A flaw was found in the Linux kernel's net/smc component. A remote attacker could exploit a race condition during the concurrent closing of an SMC listen socket. This could lead to a NULL pointer dereference or a use-after-free vulnerability in the smc_tcp_syn_recv_sock() function, potentially causing a system crash and a denial of service."], "name": "CVE-2026-23450", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2026-04-03T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-23450\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-23450\nhttps://lore.kernel.org/linux-cve-announce/2026040316-CVE-2026-23450-2437@gregkh/T"], "threat_severity": "Important"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[8270d9c21041470f58348248b9d9dcf3bf79592e,1e4f873879e075bbd4eb1c644d6933303ac5eba4)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[8270d9c21041470f58348248b9d9dcf3bf79592e,f00fc26c8a06442b225a350fe000c0a11483e6a3)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[8270d9c21041470f58348248b9d9dcf3bf79592e,cadf3da46c15523fba90d80c9955f536ee3b4023)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[8270d9c21041470f58348248b9d9dcf3bf79592e,fd7579f0a2c84ba8a7d4f206201b50dc8ddf90c2)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[8270d9c21041470f58348248b9d9dcf3bf79592e,1fab5ece76fb42a761178dcd0ebcbf578377b0dd)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[8270d9c21041470f58348248b9d9dcf3bf79592e,6d5e4538364b9ceb1ac2941a4deb86650afb3538)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "ebfee3e153f67c8b38eb94a7062ee94aa6f92708"}}], "enrichment": {"confidence": 99.0, "confidence_source": "inferred", "scores": [{"score": 99.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "Linux", "source": "cna", "vendor": "Linux"}, "product": "linux_kernel", "vendor": "linux"}, {"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "5.18"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[0,5.18)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[6.1.167,6.2.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[6.6.130,6.7.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[6.12.78,6.13.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[6.18.20,6.19.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[6.19.10,6.20.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "[7.0-rc5,*]"}}], "enrichment": {"confidence": 99.0, "confidence_source": "inferred", "scores": [{"score": 99.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "Linux", "source": "cna", "vendor": "Linux"}, "product": "linux_kernel", "vendor": "linux"}], "analysis": {"en": {"generated_at": "2026-04-28T21:45:39.847039+00:00", "value": {"mitigation_remediation": ["Apply the kernel patch that replaces smc_tcp_syn_recv_sock() with the RCU\u2011based fix.", "Reboot the system to load the updated kernel.", "Block or drop incoming SMC protocol traffic (e.g., via firewall rules) as a temporary mitigation until the kernel is updated."], "summary": {"action": "Patch Immediately", "impact": "Denial of Service via kernel crash"}, "threat_synthesis": {"affected_systems": "The issue applies to all Linux kernel builds that include the unpatched implementation of smc_tcp_syn_recv_sock(). No specific kernel release range is listed in the advisory; the patch references encompass recent stable branches, implying that any distribution running a kernel prior to the change \u2013 including common server and embedded variants \u2013 is potentially vulnerable.", "description_and_impact": "In the Linux kernel\u2019s SMC module, a race condition exists when the listening socket\u2019s user data can be cleared while another context reads it. This can result in a NULL pointer dereference or a use\u2011after\u2011free, which unconditionally triggers a kernel panic during the TCP three\u2011way handshake path. The crash brings the affected host down, effectively causing a denial\u2011of\u2011service. The vulnerability is a kernel\u2011level severity flaw that does not directly grant attacker privileges but can be leveraged to destabilize the system.", "risk_and_exploitability": "The CVSS score of 9.8 indicates a high severity. The EPSS score of <1\u2009% suggests the vulnerability is not widely observed, and it is not yet listed in CISA KEV, implying no confirmed widespread exploitation. The likely attack vector is network traffic that reaches the vulnerable SMC listening socket \u2013 for example, specially crafted SYN packets that invoke the problematic path. This requires only external network access to the host; local privileges are not required, but the target must have a listening SMC socket. Because the flaw is triggered by a race, the threat is high but the exploitation likelihood under normal conditions is considered low."}}}}, "created": "2026-04-03T21:13:47.938696+00:00", "updated": "2026-04-28T22:00:14.087002+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}