{"api_version":"1","generated_at":"2026-07-28T04:36:51+00:00","cve":"CVE-2026-64401","urls":{"html":"https://cve.report/CVE-2026-64401","api":"https://cve.report/api/cve/CVE-2026-64401.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-64401","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-64401"},"summary":{"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":"PUBLISHED","assigner":"Linux","published_at":"2026-07-25 10:17:23","updated_at":"2026-07-27 05:16:47"},"problem_types":[],"metrics":[{"version":"3.1","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","score":"7.8","severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"7.8","severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","data":{"baseScore":7.8,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/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/51d18db392e5386a7bb9e816d611f14e600cca3c","name":"https://git.kernel.org/stable/c/51d18db392e5386a7bb9e816d611f14e600cca3c","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/91b8a58c6ac15c7db6518f696389933282f88da7","name":"https://git.kernel.org/stable/c/91b8a58c6ac15c7db6518f696389933282f88da7","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/ec457f9afe5ae9538bdcd58fd4cb442b9787e183","name":"https://git.kernel.org/stable/c/ec457f9afe5ae9538bdcd58fd4cb442b9787e183","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/0700f946659d0ab2352ec8a9b1c6fc74b13a27d7","name":"https://git.kernel.org/stable/c/0700f946659d0ab2352ec8a9b1c6fc74b13a27d7","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/945b4a4a54497db1dcb2f20ef801a84e884dac21","name":"https://git.kernel.org/stable/c/945b4a4a54497db1dcb2f20ef801a84e884dac21","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/aa3c0cab4b28c5007ec570c63e1d6ad6943ed0fd","name":"https://git.kernel.org/stable/c/aa3c0cab4b28c5007ec570c63e1d6ad6943ed0fd","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-64401","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-64401","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected fed979a7e082bd9f25f9002c3c4f8740dacd0bc8 51d18db392e5386a7bb9e816d611f14e600cca3c git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected fed979a7e082bd9f25f9002c3c4f8740dacd0bc8 aa3c0cab4b28c5007ec570c63e1d6ad6943ed0fd git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected fed979a7e082bd9f25f9002c3c4f8740dacd0bc8 945b4a4a54497db1dcb2f20ef801a84e884dac21 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected fed979a7e082bd9f25f9002c3c4f8740dacd0bc8 91b8a58c6ac15c7db6518f696389933282f88da7 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 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00:07:43"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["fs/smb/client/cifs_swn.c","fs/smb/client/trace.h"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"51d18db392e5386a7bb9e816d611f14e600cca3c","status":"affected","version":"fed979a7e082bd9f25f9002c3c4f8740dacd0bc8","versionType":"git"},{"lessThan":"aa3c0cab4b28c5007ec570c63e1d6ad6943ed0fd","status":"affected","version":"fed979a7e082bd9f25f9002c3c4f8740dacd0bc8","versionType":"git"},{"lessThan":"945b4a4a54497db1dcb2f20ef801a84e884dac21","status":"affected","version":"fed979a7e082bd9f25f9002c3c4f8740dacd0bc8","versionType":"git"},{"lessThan":"91b8a58c6ac15c7db6518f696389933282f88da7","status":"affected","version":"fed979a7e082bd9f25f9002c3c4f8740dacd0bc8","versionType":"git"},{"lessThan":"0700f946659d0ab2352ec8a9b1c6fc74b13a27d7","status":"affected","version":"fed979a7e082bd9f25f9002c3c4f8740dacd0bc8","versionType":"git"},{"lessThan":"ec457f9afe5ae9538bdcd58fd4cb442b9787e183","status":"affected","version":"fed979a7e082bd9f25f9002c3c4f8740dacd0bc8","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["fs/smb/client/cifs_swn.c","fs/smb/client/trace.h"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"5.11"},{"lessThan":"5.11","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.1.*","status":"unaffected","version":"6.1.178","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.145","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.97","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.39","versionType":"semver"},{"lessThanOrEqual":"7.1.*","status":"unaffected","version":"7.1.4","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.2-rc1","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.1.178","versionStartIncluding":"5.11","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.6.145","versionStartIncluding":"5.11","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.97","versionStartIncluding":"5.11","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.39","versionStartIncluding":"5.11","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.1.4","versionStartIncluding":"5.11","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2-rc1","versionStartIncluding":"5.11","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"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."}],"metrics":[{"cvssV3_1":{"baseScore":7.8,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}}],"providerMetadata":{"dateUpdated":"2026-07-27T05:00:33.097Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/51d18db392e5386a7bb9e816d611f14e600cca3c"},{"url":"https://git.kernel.org/stable/c/aa3c0cab4b28c5007ec570c63e1d6ad6943ed0fd"},{"url":"https://git.kernel.org/stable/c/945b4a4a54497db1dcb2f20ef801a84e884dac21"},{"url":"https://git.kernel.org/stable/c/91b8a58c6ac15c7db6518f696389933282f88da7"},{"url":"https://git.kernel.org/stable/c/0700f946659d0ab2352ec8a9b1c6fc74b13a27d7"},{"url":"https://git.kernel.org/stable/c/ec457f9afe5ae9538bdcd58fd4cb442b9787e183"}],"title":"smb: client: resolve SWN tcon from live registrations","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-64401","datePublished":"2026-07-25T08:50:44.361Z","dateReserved":"2026-07-19T15:36:31.785Z","dateUpdated":"2026-07-27T05:00:33.097Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-07-25 10:17:23","lastModifiedDate":"2026-07-27 05:16:47","problem_types":[],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":1.8,"impactScore":5.9}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"64401","Ordinal":"1","Title":"smb: client: resolve SWN tcon from live registrations","CVE":"CVE-2026-64401","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"64401","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"smb: client: resolve SWN tcon from live registrations"}]}}}