{"id":"CVE-2026-64401","revision":"295162902c63450893e8d9a0c1b2099c","records":[{"revision":"295162902c63450893e8d9a0c1b2099c","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-64401","aliases":[],"title":"smb: client: resolve SWN tcon from live registrations","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: resolve SWN tcon from live registrations\n\ncifs_swn_notify() looks up a witness registration by id under\ncifs_swnreg_idr_mutex, drops the mutex, and then uses the registration's\ncached tcon pointer. That pointer is not a lifetime reference, and it is\nnot a stable representative once cifs_get_swn_reg() lets multiple tcons\nfor the same net/share name share one registration id.\n\nA same-share second mount can keep the cifs_swn_reg alive after the first\ntcon unregisters and is freed. The registration then still points at the\nfreed first tcon, so taking tc_lock or incrementing tc_count through\nswnreg->tcon only moves the use-after-free earlier. Taking tc_lock while\nholding cifs_swnreg_idr_mutex also violates the documented CIFS lock\norder.\n\nFix this by making the registration store only the stable witness\nidentity: id, net name, share name, and notify flags. When a notify\narrives, copy that identity under cifs_swnreg_idr_mutex, drop the mutex,\nthen find and pin a live witness tcon that currently matches the net/share\npair under the normal cifs_tcp_ses_lock -> tc_lock order. The notification\npath uses that pinned tcon directly and drops the reference when done.\n\nRegistration and unregister messages now use the live tcon passed by the\ncaller instead of a cached tcon in the registration. The final unregister\nsend is folded into cifs_swn_unregister() while the registration is still\nprotected by cifs_swnreg_idr_mutex. This removes the previous\nfind/drop/reacquire raw-pointer window. The release path only removes the\nidr entry and frees the stable identity strings.\n\nThis preserves the intended one-registration/many-tcon behavior: a\nregistration id represents a net/share pair, and notify handling acts on a\nlive representative selected at use time. It also preserves CLIENT_MOVE\nordering for the representative tcon because the old-IP unregister is sent\nbefore cifs_swn_register() sends the new-IP register.","state":0,"publishedAt":"2026-07-25T08:50:44.361+00:00","modifiedAt":"2026-10-19T20:38:26.985+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"unaffected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"fs/smb/client/cifs_swn.c\",\n \"fs/smb/client/trace.h\"\n ],\n \"versions\": [\n {\n \"version\": \"fed979a7e082bd9f25f9002c3c4f8740dacd0bc8\",\n \"lessThan\": \"51d18db392e5386a7bb9e816d611f14e600cca3c\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"fed979a7e082bd9f25f9002c3c4f8740dacd0bc8\",\n \"lessThan\": \"aa3c0cab4b28c5007ec570c63e1d6ad6943ed0fd\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"fed979a7e082bd9f25f9002c3c4f8740dacd0bc8\",\n \"lessThan\": \"945b4a4a54497db1dcb2f20ef801a84e884dac21\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"fed979a7e082bd9f25f9002c3c4f8740dacd0bc8\",\n \"lessThan\": \"91b8a58c6ac15c7db6518f696389933282f88da7\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"fed979a7e082bd9f25f9002c3c4f8740dacd0bc8\",\n \"lessThan\": \"0700f946659d0ab2352ec8a9b1c6fc74b13a27d7\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"fed979a7e082bd9f25f9002c3c4f8740dacd0bc8\",\n \"lessThan\": \"ec457f9afe5ae9538bdcd58fd4cb442b9787e183\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n }\n ]\n }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"affected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"fs/smb/client/cifs_swn.c\",\n \"fs/smb/client/trace.h\"\n ],\n \"versions\": [\n {\n \"version\": \"5.11\",\n \"status\": \"affected\"\n },\n {\n \"version\": \"0\",\n \"lessThan\": \"5.11\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.1.178\",\n \"lessThanOrEqual\": \"6.1.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.6.145\",\n \"lessThanOrEqual\": \"6.6.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.12.97\",\n \"lessThanOrEqual\": \"6.12.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.18.39\",\n \"lessThanOrEqual\": \"6.18.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.1.4\",\n \"lessThanOrEqual\": \"7.1.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.2\",\n \"lessThanOrEqual\": \"*\",\n \"status\": \"unaffected\",\n \"versionType\": \"original_commit_for_fix\"\n }\n ]\n }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8,"severity":"HIGH"}],"references":["https://git.kernel.org/stable/c/51d18db392e5386a7bb9e816d611f14e600cca3c","https://git.kernel.org/stable/c/aa3c0cab4b28c5007ec570c63e1d6ad6943ed0fd","https://git.kernel.org/stable/c/945b4a4a54497db1dcb2f20ef801a84e884dac21","https://git.kernel.org/stable/c/91b8a58c6ac15c7db6518f696389933282f88da7","https://git.kernel.org/stable/c/0700f946659d0ab2352ec8a9b1c6fc74b13a27d7","https://git.kernel.org/stable/c/ec457f9afe5ae9538bdcd58fd4cb442b9787e183"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-64401","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-64401","identifiers":["CVE-2026-64401"]},"retained":false,"historicalAffected":[]}],"coverage":[]}