{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-64401","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-07-19T15:36:31.785Z","datePublished":"2026-07-25T08:50:44.361Z","dateUpdated":"2026-08-17T04:54:59.017Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-17T04:54:59.017Z"},"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":{"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"},"scenarios":[{"lang":"en","value":"AV:L - The UAF is locally reachable through the world-readable /proc/fs/cifs/DebugData path and, on earlier affected kernels, unrestricted SWN generic-netlink notifications.\nAC:L - A same-share second mount deterministically preserves the registration after the first tcon is freed; repeated proc reads or notifications then dereference the stale pointer without requiring an uncontrollable race.\nPR:L - An unprivileged local user can read /proc/fs/cifs/DebugData, and affected kernels predating the companion netlink authorization fix also allowed unprivileged SWN_NOTIFY messages. User namespaces do not grant CIFS mount authority, but no mount privilege is needed once normal mount turnover creates the stale registration.\nUI:N - Once a witness-enabled registration exists, exploitation requires no further victim action; the attacker can invoke the local trigger directly.\nS:U - Successful exploitation compromises the host kernel within the same security authority and does not inherently cross a VM, IOMMU, or other scope boundary.\nC:H - The heap UAF involves attacker-reclaimable cifs_tcon and cifs_swn_reg objects whose pointer chains reach session credentials and arbitrary kernel memory, enabling high-impact disclosure primitives.\nI:H - Reclaiming the freed objects can redirect client-move and reconnect operations through attacker-influenced pointers, providing arbitrary-write and control-flow-hijacking potential.\nA:H - Dereferencing the freed tcon or registration can cause an immediate kernel oops or panic, and the periodic echo worker can repeatedly exercise the stale pointer."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/client/cifs_swn.c","fs/smb/client/trace.h"],"versions":[{"version":"fed979a7e082bd9f25f9002c3c4f8740dacd0bc8","lessThan":"51d18db392e5386a7bb9e816d611f14e600cca3c","status":"affected","versionType":"git"},{"version":"fed979a7e082bd9f25f9002c3c4f8740dacd0bc8","lessThan":"aa3c0cab4b28c5007ec570c63e1d6ad6943ed0fd","status":"affected","versionType":"git"},{"version":"fed979a7e082bd9f25f9002c3c4f8740dacd0bc8","lessThan":"945b4a4a54497db1dcb2f20ef801a84e884dac21","status":"affected","versionType":"git"},{"version":"fed979a7e082bd9f25f9002c3c4f8740dacd0bc8","lessThan":"91b8a58c6ac15c7db6518f696389933282f88da7","status":"affected","versionType":"git"},{"version":"fed979a7e082bd9f25f9002c3c4f8740dacd0bc8","lessThan":"0700f946659d0ab2352ec8a9b1c6fc74b13a27d7","status":"affected","versionType":"git"},{"version":"fed979a7e082bd9f25f9002c3c4f8740dacd0bc8","lessThan":"ec457f9afe5ae9538bdcd58fd4cb442b9787e183","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/client/cifs_swn.c","fs/smb/client/trace.h"],"versions":[{"version":"5.11","status":"affected"},{"version":"0","lessThan":"5.11","status":"unaffected","versionType":"semver"},{"version":"6.1.178","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.145","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.97","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.39","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.1.4","lessThanOrEqual":"7.1.*","status":"unaffected","versionType":"semver"},{"version":"7.2","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.11","versionEndExcluding":"6.1.178"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.11","versionEndExcluding":"6.6.145"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.11","versionEndExcluding":"6.12.97"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.11","versionEndExcluding":"6.18.39"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.11","versionEndExcluding":"7.1.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.11","versionEndExcluding":"7.2"}]}]}],"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"}}}}