CVE-2026-97562 (GCVE-0-2026-97562)
Vulnerability from cvelistv5 – Published: 2026-09-25 10:21 – Updated: 2026-10-19 09:09
VLAI
EPSS
VEX
Title
smb: client: pin DFS superblock in iterator callback
Summary
In the Linux kernel, the following vulnerability has been resolved:
smb: client: pin DFS superblock in iterator callback
tcon_super_cb() stores a raw superblock pointer, but __cifs_get_super()
takes its active reference only after iterate_supers_type() has dropped
s_umount and its passive reference. Concurrent DFS automount expiry can
therefore free the superblock before cifs_sb_active() uses it.
A deterministic KASAN test reproduces the race as:
BUG: KASAN: slab-use-after-free in cifs_sb_active+0x77/0x80
The same test passes with this change applied.
Take the active reference in the callback while iterate_supers_type()
still holds s_umount shared. cifs_put_tcp_super() remains the matching
release.
Severity
7.5 (High)
Assigner
References
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
bacd704a95ad0b93af995aae4a523aa046f46563 , < 3c9acc9835c304013a4faeb969fe9333d66ca9f8
(git)
Affected: bacd704a95ad0b93af995aae4a523aa046f46563 , < ea43a15cea36dc5ddd832be5bddeac7dd804cbcf (git) Affected: bacd704a95ad0b93af995aae4a523aa046f46563 , < a6b6561522212af852c9ad8a7dca8d59ef2c7377 (git) Affected: bacd704a95ad0b93af995aae4a523aa046f46563 , < 5b01a8c0209690db75341528ec53fd87e0ac1460 (git) Affected: bacd704a95ad0b93af995aae4a523aa046f46563 , < d806d5a85dcbe2a0f181b2f0f9f61ddfbefa1818 (git) |
guessed | |
| Linux | Linux |
Affected:
5.7
Unaffected: 0 , < 5.7 (semver) Unaffected: 6.6.158 , ≤ 6.6.* (semver) Unaffected: 6.12.111 , ≤ 6.12.* (semver) Unaffected: 6.18.53 , ≤ 6.18.* (semver) Unaffected: 7.2.7 , ≤ 7.2.* (semver) Unaffected: 7.3 , ≤ * (original_commit_for_fix) |
guessed |
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"programFiles": [
"fs/smb/client/misc.c"
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"versions": [
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{
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"status": "unaffected",
"version": "0",
"versionType": "semver"
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"status": "unaffected",
"version": "6.6.158",
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{
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"status": "unaffected",
"version": "6.12.111",
"versionType": "semver"
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{
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"version": "6.18.53",
"versionType": "semver"
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{
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"version": "7.2.7",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.158",
"versionStartIncluding": "5.7",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.111",
"versionStartIncluding": "5.7",
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{
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{
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"negate": false,
"operator": "OR"
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],
"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."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 7.5,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"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() -\u003e cifs_tree_connect() -\u003e cifs_get_dfs_tcon_super() -\u003e __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\u0027s session. Forcing the client\u0027s 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-\u003eprepath 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": {
"dateUpdated": "2026-10-19T09:09:25.220Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
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"url": "https://git.kernel.org/stable/c/3c9acc9835c304013a4faeb969fe9333d66ca9f8"
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{
"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"
}
],
"title": "smb: client: pin DFS superblock in iterator callback",
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"assignerShortName": "Linux",
"cveId": "CVE-2026-97562",
"datePublished": "2026-09-25T10:21:50.664Z",
"dateReserved": "2026-09-24T16:01:01.155Z",
"dateUpdated": "2026-10-19T09:09:25.220Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-97562",
"date": "2026-11-14",
"epss": "0.00413",
"percentile": "0.36163"
},
"microsoft_vex": {
"current_release_date": "2026-10-21T18:38:23.000Z",
"cve": "CVE-2026-97562",
"id": "msrc_CVE-2026-97562",
"initial_release_date": "2026-09-28T00:09:28.000Z",
"product_status:fixed": "1",
"product_status:known_affected": "1",
"product_status:under_investigation": "1",
"source": "Microsoft CSAF VEX",
"status": "final",
"title": "smb: client: pin DFS superblock in iterator callback",
"url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-97562.json",
"version": "4"
},
"nvd": {
"cve": {
"affected": [
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"product": "Linux",
"programFiles": [
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],
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"vendor": "Linux",
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"version": "6.18.53",
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"version": "7.2.7",
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"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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],
"cveTags": [],
"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."
}
],
"id": "CVE-2026-97562",
"lastModified": "2026-10-19T10:17:25.280",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "HIGH",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 7.5,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "REQUIRED",
"vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H",
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"impactScore": 5.9,
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"type": "Secondary"
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"published": "2026-09-25T11:17:06.757",
"references": [
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"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/3c9acc9835c304013a4faeb969fe9333d66ca9f8"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/5b01a8c0209690db75341528ec53fd87e0ac1460"
},
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],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Received"
}
},
"redhat_vex": {
"aggregate_severity": "Moderate",
"current_release_date": "2026-11-06T02:27:31+00:00",
"cve": "CVE-2026-97562",
"id": "CVE-2026-97562",
"initial_release_date": "2026-09-25T00:00:00+00:00",
"product_status:known_affected": "161",
"product_status:known_not_affected": "42",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "kernel: smb: client: pin DFS superblock in iterator callback",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-97562.json",
"version": "3"
}
}
}
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Sightings
| Author | Source | Type | Date | Other |
|---|
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
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The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.