{"id":"CVE-2026-97562","state":"PUBLISHED","title":"smb: client: pin DFS superblock in iterator callback","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: pin DFS superblock in iterator callback\n\ntcon_super_cb() stores a raw superblock pointer, but __cifs_get_super()\ntakes its active reference only after iterate_supers_type() has dropped\ns_umount and its passive reference. Concurrent DFS automount expiry can\ntherefore free the superblock before cifs_sb_active() uses it.\n\nA deterministic KASAN test reproduces the race as:\n\n  BUG: KASAN: slab-use-after-free in cifs_sb_active+0x77/0x80\n\nThe same test passes with this change applied.\n\nTake the active reference in the callback while iterate_supers_type()\nstill holds s_umount shared. cifs_put_tcp_super() remains the matching\nrelease.","publishedAt":"2026-09-25T10:21:50.664Z","updatedAt":"2026-10-19T09:09:25.220Z","severity":{"score":7.5,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"bacd704a95ad0b93af995aae4a523aa046f46563","status":"affected","lessThan":"3c9acc9835c304013a4faeb969fe9333d66ca9f8","versionType":"git"},{"version":"bacd704a95ad0b93af995aae4a523aa046f46563","status":"affected","lessThan":"ea43a15cea36dc5ddd832be5bddeac7dd804cbcf","versionType":"git"},{"version":"bacd704a95ad0b93af995aae4a523aa046f46563","status":"affected","lessThan":"a6b6561522212af852c9ad8a7dca8d59ef2c7377","versionType":"git"},{"version":"bacd704a95ad0b93af995aae4a523aa046f46563","status":"affected","lessThan":"5b01a8c0209690db75341528ec53fd87e0ac1460","versionType":"git"},{"version":"bacd704a95ad0b93af995aae4a523aa046f46563","status":"affected","lessThan":"d806d5a85dcbe2a0f181b2f0f9f61ddfbefa1818","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/client/misc.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.7","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.7","versionType":"semver"},{"version":"6.6.158","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.111","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.53","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.7","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/client/misc.c"]}],"references":["https://git.kernel.org/stable/c/3c9acc9835c304013a4faeb969fe9333d66ca9f8","https://git.kernel.org/stable/c/ea43a15cea36dc5ddd832be5bddeac7dd804cbcf","https://git.kernel.org/stable/c/a6b6561522212af852c9ad8a7dca8d59ef2c7377","https://git.kernel.org/stable/c/5b01a8c0209690db75341528ec53fd87e0ac1460","https://git.kernel.org/stable/c/d806d5a85dcbe2a0f181b2f0f9f61ddfbefa1818"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:43.249Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/97xxx/CVE-2026-97562.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-97562","state":"PUBLISHED","datePublished":"2026-09-25T10:21:50.664Z","dateUpdated":"2026-10-19T09:09:25.220Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-24T16:01:01.155Z"},"containers":{"cna":{"title":"smb: client: pin DFS superblock in iterator callback","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: pin DFS superblock in iterator callback\n\ntcon_super_cb() stores a raw superblock pointer, but __cifs_get_super()\ntakes its active reference only after iterate_supers_type() has dropped\ns_umount and its passive reference. Concurrent DFS automount expiry can\ntherefore free the superblock before cifs_sb_active() uses it.\n\nA deterministic KASAN test reproduces the race as:\n\n  BUG: KASAN: slab-use-after-free in cifs_sb_active+0x77/0x80\n\nThe same test passes with this change applied.\n\nTake the active reference in the callback while iterate_supers_type()\nstill holds s_umount shared. cifs_put_tcp_super() remains the matching\nrelease."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"bacd704a95ad0b93af995aae4a523aa046f46563","status":"affected","lessThan":"3c9acc9835c304013a4faeb969fe9333d66ca9f8","versionType":"git"},{"version":"bacd704a95ad0b93af995aae4a523aa046f46563","status":"affected","lessThan":"ea43a15cea36dc5ddd832be5bddeac7dd804cbcf","versionType":"git"},{"version":"bacd704a95ad0b93af995aae4a523aa046f46563","status":"affected","lessThan":"a6b6561522212af852c9ad8a7dca8d59ef2c7377","versionType":"git"},{"version":"bacd704a95ad0b93af995aae4a523aa046f46563","status":"affected","lessThan":"5b01a8c0209690db75341528ec53fd87e0ac1460","versionType":"git"},{"version":"bacd704a95ad0b93af995aae4a523aa046f46563","status":"affected","lessThan":"d806d5a85dcbe2a0f181b2f0f9f61ddfbefa1818","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/client/misc.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.7","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.7","versionType":"semver"},{"version":"6.6.158","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.111","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.53","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.7","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/client/misc.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/3c9acc9835c304013a4faeb969fe9333d66ca9f8"},{"url":"https://git.kernel.org/stable/c/ea43a15cea36dc5ddd832be5bddeac7dd804cbcf"},{"url":"https://git.kernel.org/stable/c/a6b6561522212af852c9ad8a7dca8d59ef2c7377"},{"url":"https://git.kernel.org/stable/c/5b01a8c0209690db75341528ec53fd87e0ac1460"},{"url":"https://git.kernel.org/stable/c/d806d5a85dcbe2a0f181b2f0f9f61ddfbefa1818"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H","baseScore":7.5,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - The racing side is started by the remote SMB server: dropping the session or replying STATUS_NETWORK_NAME_DELETED makes the client run smb2_reconnect() -> cifs_tree_connect() -> cifs_get_dfs_tcon_super() -> __cifs_get_super(). There, tcon_super_cb() saves a raw superblock pointer that is used after s_umount is released.\nAC:H - The server can force reconnects repeatedly, but the superblock is only freed if a DFS-link automount expires via cifs_expire_automounts() (a 500s periodic timer, idle submount only) inside the small gap between iterate_supers_type() returning and cifs_sb_active(). The attacker does not control that timing.\nPR:N - The attacker is the SMB/DFS server or a network peer that can reset the client's session. Forcing the client's tree reconnect needs no account or privilege on the client.\nUI:R - A victim must have mounted a DFS share with an automounted DFS link from the attacker-reachable server (cifs mounts need real CAP_SYS_ADMIN, not a user namespace), and the link must be idle long enough to expire.\nS:U - The use-after-free corrupts memory in the same kernel that runs the CIFS client, so no separate security authority is crossed.\nC:H - After the freed super_block and cifs_sb_info are reused, the reconnect path keeps reading them (cifs_sb_active() on freed memory, then CIFS_SB(sb) fields in tree_connect_dfs_target()), so reclaimed slab contents can be read.\nI:H - cifs_sb_active() increments counters in the freed cifs_sb/sb, and cifs_update_super_prepath() frees and replaces cifs_sb->prepath in the freed cifs_sb_info. Both are writes into freed memory that can be turned into heap corruption.\nA:H - The fix commit reports a KASAN slab-use-after-free in cifs_sb_active(); without KASAN the corrupted superblock refcounts and the later cifs_put_tcp_super()/deactivate_super() can crash the kernel."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T09:09:25.220Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"6.6.158"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"6.12.111"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"6.18.53"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"7.2.7"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}