{"api_version":"1","generated_at":"2026-10-27T03:18:28+00:00","cve":"CVE-2026-98870","urls":{"html":"https://cve.report/CVE-2026-98870","api":"https://cve.report/api/cve/CVE-2026-98870.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-98870","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-98870"},"summary":{"title":"ksmbd: remove stale channels from all sessions on teardown","description":"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.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-10-23 12:18:20","updated_at":"2026-10-24 14:16:47"},"problem_types":[],"metrics":[{"version":"3.1","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","score":"8.8","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","data":{"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","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"8.8","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","data":{"baseScore":8.8,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}}],"references":[{"url":"https://git.kernel.org/stable/c/b10665730fbf6b5e45fe422badcbbc3f0df96ef5","name":"https://git.kernel.org/stable/c/b10665730fbf6b5e45fe422badcbbc3f0df96ef5","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/a15cae16f4432a5ad919ee633e31b07178492955","name":"https://git.kernel.org/stable/c/a15cae16f4432a5ad919ee633e31b07178492955","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/f8200bb4994e65a2e5c5b314789eeae39078619d","name":"https://git.kernel.org/stable/c/f8200bb4994e65a2e5c5b314789eeae39078619d","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/9cd6d714d3ca0cff296542dc989696884e41970f","name":"https://git.kernel.org/stable/c/9cd6d714d3ca0cff296542dc989696884e41970f","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/b145f9b56c87f9c23ad5464ab0844dbc1de12b36","name":"https://git.kernel.org/stable/c/b145f9b56c87f9c23ad5464ab0844dbc1de12b36","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-98870","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98870","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected b1b6ed903a6e2b3505a48706bcd499b447ef9e44 f8200bb4994e65a2e5c5b314789eeae39078619d git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 47b018dba6ec7ebf403fd2d1e713bc7acc9bbb23 9cd6d714d3ca0cff296542dc989696884e41970f git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 9ef4dfd5edbd02f4bf10cd420a30896093d98a67 b145f9b56c87f9c23ad5464ab0844dbc1de12b36 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 5a5b0b7a01fe19b383b3c046546b5ae30c1a7d71 a15cae16f4432a5ad919ee633e31b07178492955 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected faf8578c77f3d846aca9cd882c293e03eafcc6df b10665730fbf6b5e45fe422badcbbc3f0df96ef5 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected e632f21a8bc0c59abc4960482836ac3782db93c0 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 5.15.222 5.16 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["fs/smb/server/mgmt/user_session.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"f8200bb4994e65a2e5c5b314789eeae39078619d","status":"affected","version":"b1b6ed903a6e2b3505a48706bcd499b447ef9e44","versionType":"git"},{"lessThan":"9cd6d714d3ca0cff296542dc989696884e41970f","status":"affected","version":"47b018dba6ec7ebf403fd2d1e713bc7acc9bbb23","versionType":"git"},{"lessThan":"b145f9b56c87f9c23ad5464ab0844dbc1de12b36","status":"affected","version":"9ef4dfd5edbd02f4bf10cd420a30896093d98a67","versionType":"git"},{"lessThan":"a15cae16f4432a5ad919ee633e31b07178492955","status":"affected","version":"5a5b0b7a01fe19b383b3c046546b5ae30c1a7d71","versionType":"git"},{"lessThan":"b10665730fbf6b5e45fe422badcbbc3f0df96ef5","status":"affected","version":"faf8578c77f3d846aca9cd882c293e03eafcc6df","versionType":"git"},{"status":"affected","version":"e632f21a8bc0c59abc4960482836ac3782db93c0","versionType":"git"},{"lessThan":"5.16","status":"affected","version":"5.15.222","versionType":"semver"}]},{"defaultStatus":"unaffected","product":"Linux","programFiles":["fs/smb/server/mgmt/user_session.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux"}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15.222","vulnerable":true}],"negate":false,"operator":"OR"}]}],"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":{"baseScore":8.8,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"},"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."}]}],"providerMetadata":{"dateUpdated":"2026-10-24T14:09:26.805Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"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"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-98870","datePublished":"2026-10-23T11:37:07.113Z","dateReserved":"2026-09-25T10:25:14.377Z","dateUpdated":"2026-10-24T14:09:26.805Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-10-23 12:18:20","lastModifiedDate":"2026-10-24 14:16:47","problem_types":[],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","cvssData":{"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","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":2.8,"impactScore":5.9}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"98870","Ordinal":"1","Title":"ksmbd: remove stale channels from all sessions on teardown","CVE":"CVE-2026-98870","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"98870","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"ksmbd: remove stale channels from all sessions on teardown"}]}}}