{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-98870", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-25T10:25:14.377Z", "datePublished": "2026-10-23T11:37:07.113Z", "dateUpdated": "2026-10-24T14:09:26.805Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-24T14:09:26.805Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: remove stale channels from all sessions on teardown\n\nksmbd_sessions_deregister() removes a connection's channels from other\nsessions' channel lists only while conn->binding is still set:\n\n\tif (conn->binding) {\n\t\thash_for_each_safe(sessions_table, ...)\n\t\t\tksmbd_chann_del(conn, sess);\n\t}\n\nconn->binding is a transient flag: it is cleared once a binding\nSESSION_SETUP completes, and also by a subsequent non-binding\nSESSION_SETUP on the same connection (a reauthentication on a bound\nchannel, or a new SessionId==0 setup). A connection that has bound a\nchannel into another session's ksmbd_chann_list and then clears\nconn->binding leaves that channel behind when it disconnects: the\nchannel, whose chann->conn points at the now freed struct ksmbd_conn,\nstays on the owner session's list.\n\nWhen the owning connection later tears down, the second loop\ndereferences the stale channel:\n\n\txa_for_each(&sess->ksmbd_chann_list, chann_id, chann)\n\t\tif (chann->conn != conn)\n\t\t\tksmbd_conn_set_exiting(chann->conn); /* freed */\n\nwhich is a use-after-free write into the freed ksmbd_conn (the same\nstale channel is also walked by show_proc_session() through /proc). The\nsession is leaked as well, because its channel list never empties.\n\nRemove the conn->binding gate so a connection always removes its\nchannels from every session on teardown." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 8.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:N - TCP/445 SMB2 SESSION_SETUP messages carry SessionId and SMB2_SESSION_REQ_FLAG_BINDING into smb2_sess_setup(), which calls register_session_channel(); TCP teardown then reaches patched ksmbd_sessions_deregister() through ksmbd_server_terminate_conn().\nAC:L - On a multichannel-enabled server, one client can bind a second connection, send a non-binding SESSION_SETUP to clear conn->binding, close it, wait for its ksmbd_conn to be freed, then close the owning connection; no race or third-party state is needed.\nPR:L - smb2_sess_setup() rejects guest binding and requires a valid session; ntlm_authenticate() compares the session user and ksmbd_decode_ntlmssp_auth_blob() verifies the NTLMv2 response before register_session_channel(), requiring valid non-guest SMB credentials.\nUI:N - After authentication, the SMB client alone sends both SESSION_SETUP variants and closes the bound and owning TCP connections; no victim action is required.\nS:U - register_session_channel() stores a kernel ksmbd_conn pointer in a kernel ksmbd_session, and the stale-pointer write in ksmbd_sessions_deregister() corrupts resources within that same kernel security authority.\nC:H - register_session_channel() leaves channel::conn pointing to a freed kmalloc-backed ksmbd_conn; remotely groomed slab reuse followed by the stale dereference creates exploitable kernel memory corruption that can lead to arbitrary kernel-data disclosure.\nI:H - During owner teardown, ksmbd_sessions_deregister() passes the dangling chann->conn to ksmbd_conn_set_exiting(), writing KSMBD_SESS_EXITING into a reused slab object; this UAF corruption can be groomed for kernel data modification or control-flow hijacking.\nA:H - The stale write can corrupt a live slab object and cause an oops or panic; if the slot is reused by another ksmbd_conn, changing its status to KSMBD_SESS_EXITING also terminates that connection, and the sequence is repeatable." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/smb/server/mgmt/user_session.c" ], "versions": [ { "version": "b1b6ed903a6e2b3505a48706bcd499b447ef9e44", "lessThan": "f8200bb4994e65a2e5c5b314789eeae39078619d", "status": "affected", "versionType": "git" }, { "version": "47b018dba6ec7ebf403fd2d1e713bc7acc9bbb23", "lessThan": "9cd6d714d3ca0cff296542dc989696884e41970f", "status": "affected", "versionType": "git" }, { "version": "9ef4dfd5edbd02f4bf10cd420a30896093d98a67", "lessThan": "b145f9b56c87f9c23ad5464ab0844dbc1de12b36", "status": "affected", "versionType": "git" }, { "version": "5a5b0b7a01fe19b383b3c046546b5ae30c1a7d71", "lessThan": "a15cae16f4432a5ad919ee633e31b07178492955", "status": "affected", "versionType": "git" }, { "version": "faf8578c77f3d846aca9cd882c293e03eafcc6df", "lessThan": "b10665730fbf6b5e45fe422badcbbc3f0df96ef5", "status": "affected", "versionType": "git" }, { "version": "e632f21a8bc0c59abc4960482836ac3782db93c0", "status": "affected", "versionType": "git" }, { "version": "5.15.222", "lessThan": "5.16", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/smb/server/mgmt/user_session.c" ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15.222" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/f8200bb4994e65a2e5c5b314789eeae39078619d" }, { "url": "https://git.kernel.org/stable/c/9cd6d714d3ca0cff296542dc989696884e41970f" }, { "url": "https://git.kernel.org/stable/c/b145f9b56c87f9c23ad5464ab0844dbc1de12b36" }, { "url": "https://git.kernel.org/stable/c/a15cae16f4432a5ad919ee633e31b07178492955" }, { "url": "https://git.kernel.org/stable/c/b10665730fbf6b5e45fe422badcbbc3f0df96ef5" } ], "title": "ksmbd: remove stale channels from all sessions on teardown", "x_generator": { "engine": "bippy-1.2.0" } } } }