{"id":"CVE-2026-72422","summary":"ksmbd: fix use-after-free of conn-\u003epreauth_info in concurrent SMB2 NEGOTIATE","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix use-after-free of conn-\u003epreauth_info in concurrent SMB2 NEGOTIATE\n\nconn-\u003epreauth_info is shared connection state (struct\npreauth_integrity_info, kmalloc-96) that is allocated and freed by the\nSMB2 NEGOTIATE handler and read by the response send path.\n\nsmb2_handle_negotiate() allocates conn-\u003epreauth_info, and on a\ndeassemble_neg_contexts() failure kfrees it and sets it to NULL. Both the\nallocation and the free/NULL happen under ksmbd_conn_lock(conn) (the\nconnection srv_mutex), which is held across the whole handler body.\n\nThe response send path smb3_preauth_hash_rsp(), called from the send:\nblock of __handle_ksmbd_work(), reads conn-\u003epreauth_info and dereferences\nconn-\u003epreauth_info-\u003ePreauth_HashValue (via\nksmbd_gen_preauth_integrity_hash()) without taking conn_lock. When a\nclient drives two SMB2 NEGOTIATE requests on the same connection, one\nworker can free conn-\u003epreauth_info on the failing-negotiate path while a\nconcurrent send-path worker is reading it, producing a slab\nuse-after-free read (KASAN-confirmed).\n\nThe send-path read tested conn-\u003epreauth_info for NULL but raced with the\nfree that occurs between the NULL check and the dereference, so the NULL\nguard alone does not close the window.\n\nSerialize the NEGOTIATE-branch read in smb3_preauth_hash_rsp() under\nksmbd_conn_lock(conn) and re-check conn-\u003epreauth_info inside the lock.\nBecause the negotiate handler holds conn_lock across its kfree + NULL\nassignment, a reader that also takes conn_lock either runs fully before\nthe allocation or fully after the NULL store, and can never observe the\nfreed-but-not-yet-NULLed pointer. ksmbd_gen_preauth_integrity_hash()\ntakes no locks itself (it only computes a SHA-512 over the buffer), so\nno lock-ordering inversion is introduced, and conn_lock is a sleepable\nmutex which is safe on this send path (it already performs network I/O).","modified":"2026-10-08T02:51:47.949631305Z","published":"2026-08-15T05:56:41.090Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72422.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/0c054227479ed7e36ebccb3a558bc0ef698264f6"},{"type":"WEB","url":"https://git.kernel.org/stable/c/16a1ecf39c217e3d164bd32ef2a4f650abc067fa"},{"type":"WEB","url":"https://git.kernel.org/stable/c/1c89da3baa2b1f269178afa87dc30479b8535776"},{"type":"WEB","url":"https://git.kernel.org/stable/c/7470511d085af1c7a043a60e53d52b512d5a10b1"},{"type":"WEB","url":"https://git.kernel.org/stable/c/77bb0bbfcc4e777ca653174689e5e363f8ee63d1"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c7bef84740d1d57848c74f6f5b996606e43ea4fe"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d0a469122e7bf8338fec1949fb1e8e1290ed8caa"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72422.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-72422"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"dd4e4c811898410e6a3ae3b63207b7c542860907"},{"fixed":"c7bef84740d1d57848c74f6f5b996606e43ea4fe"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"aa7253c2393f6dcd6a1468b0792f6da76edad917"},{"fixed":"d0a469122e7bf8338fec1949fb1e8e1290ed8caa"},{"fixed":"7470511d085af1c7a043a60e53d52b512d5a10b1"},{"fixed":"16a1ecf39c217e3d164bd32ef2a4f650abc067fa"},{"fixed":"77bb0bbfcc4e777ca653174689e5e363f8ee63d1"},{"fixed":"1c89da3baa2b1f269178afa87dc30479b8535776"},{"fixed":"0c054227479ed7e36ebccb3a558bc0ef698264f6"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"5.15.61"},{"fixed":"5.15.212"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"5.18.18"},{"fixed":"5.19"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"5.19.2"},{"fixed":"5.20"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"8a8315a5960bd2b5ffc75f44fc089e57c3b17c44"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"ff20f1875889dbe4a67c9298e609d7c88cf6456d"}]}],"versions":["v5.15.211","v5.15.210","v5.15.209","v5.15.208","v5.15.207","v5.15.206","v5.15.205","v5.15.204","v5.15.203","v5.15.202","v5.15.201","v5.15.200","v5.15.199","v5.15.198","v5.15.197","v5.15.196","v5.15.195","v5.15.194","v5.15.193","v5.15.192","v5.15.191","v5.15.190","v5.15.189","v5.15.188","v5.15.187","v5.15.186","v5.15.185","v5.15.184","v5.15.183","v5.15.182","v5.15.181","v5.15.180","v5.15.179","v5.15.178","v5.15.177","v5.15.176","v5.15.175","v5.15.174","v5.15.173","v5.15.172","v5.15.171","v5.15.170","v5.15.169","v5.15.168","v5.15.167","v5.15.166","v5.15.165","v5.15.164","v5.15.163","v5.15.162","v5.15.161","v5.15.160","v5.15.159","v5.15.158","v5.15.157","v5.15.156","v5.15.155","v5.15.154","v5.15.153","v5.15.152","v5.15.151","v5.15.150","v5.15.149","v5.15.148","v5.15.147","v5.15.146","v5.15.145","v5.15.144","v5.15.143","v5.15.142","v5.15.141","v5.15.140","v5.15.139","v5.15.138","v5.15.137","v5.15.136","v5.15.135","v5.15.134","v5.15.133","v5.15.132","v5.15.131","v5.15.130","v5.15.129","v5.15.128","v5.15.127","v5.15.126","v5.15.125","v5.15.124","v5.15.123","v5.15.122","v5.15.121","v5.15.120","v5.15.119","v5.15.118","v5.15.117","v5.15.116","v5.15.115","v5.15.114","v5.15.113","v5.15.112","v5.15.111","v5.15.110","v5.15.109","v5.15.108","v5.15.107","v5.15.106","v5.15.105","v5.15.104","v5.15.103","v5.15.102","v5.15.101","v5.15.100","v5.15.99","v5.15.98","v5.15.97","v5.15.96","v5.15.95","v5.15.94","v5.15.93","v5.15.92","v5.15.91","v5.15.90","v5.15.89","v5.15.88","v5.15.87","v5.15.86","v5.15.85","v5.15.84","v5.15.83","v5.15.82","v5.15.81","v5.15.80","v5.15.79","v5.15.78","v5.15.77","v5.15.76","v5.15.75","v5.15.74","v5.15.73","v5.15.72","v5.15.71","v5.15.70","v5.15.69","v5.15.68","v5.15.67","v5.15.66","v5.15.65","v5.15.64","v5.15.63","v5.15.62","v5.15.61","v5.18.19","v5.18.18","v5.19.17","v5.19.16","v5.19.15","v5.19.14","v5.19.13","v5.19.12","v5.19.11","v5.19.10","v5.19.9","v5.19.8","v5.19.7","v5.19.6","v5.19.5","v5.19.4","v5.19.3","v5.19.2"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-72422.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.15.212"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.178"}]},{"type":"ECOSYSTEM","events":[{"i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