CVE-2025-40320 (GCVE-0-2025-40320)
Vulnerability from cvelistv5 – Published: 2025-12-08 00:46 – Updated: 2026-08-05 12:09
VLAI
EPSS
VEX
Title
smb: client: fix potential cfid UAF in smb2_query_info_compound
Summary
In the Linux kernel, the following vulnerability has been resolved:
smb: client: fix potential cfid UAF in smb2_query_info_compound
When smb2_query_info_compound() retries, a previously allocated cfid may
have been freed in the first attempt.
Because cfid wasn't reset on replay, later cleanup could act on a stale
pointer, leading to a potential use-after-free.
Reinitialize cfid to NULL under the replay label.
Example trace (trimmed):
refcount_t: underflow; use-after-free.
WARNING: CPU: 1 PID: 11224 at ../lib/refcount.c:28 refcount_warn_saturate+0x9c/0x110
[...]
RIP: 0010:refcount_warn_saturate+0x9c/0x110
[...]
Call Trace:
<TASK>
smb2_query_info_compound+0x29c/0x5c0 [cifs f90b72658819bd21c94769b6a652029a07a7172f]
? step_into+0x10d/0x690
? __legitimize_path+0x28/0x60
smb2_queryfs+0x6a/0xf0 [cifs f90b72658819bd21c94769b6a652029a07a7172f]
smb311_queryfs+0x12d/0x140 [cifs f90b72658819bd21c94769b6a652029a07a7172f]
? kmem_cache_alloc+0x18a/0x340
? getname_flags+0x46/0x1e0
cifs_statfs+0x9f/0x2b0 [cifs f90b72658819bd21c94769b6a652029a07a7172f]
statfs_by_dentry+0x67/0x90
vfs_statfs+0x16/0xd0
user_statfs+0x54/0xa0
__do_sys_statfs+0x20/0x50
do_syscall_64+0x58/0x80
Severity
9.8 (Critical)
Assigner
References
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
433042a91f9373241307725b52de573933ffedbf , < 939c4e33005e2a56ea8fcedddf0da92df864bd3b
(git)
Affected: 4f1fffa2376922f3d1d506e49c0fd445b023a28e , < 327f89c21601ebb7889f8c97754b76f08ce95a0c (git) Affected: 4f1fffa2376922f3d1d506e49c0fd445b023a28e , < b556c278d43f4707a9073ca74d55581b4f279806 (git) Affected: 4f1fffa2376922f3d1d506e49c0fd445b023a28e , < 5c76f9961c170552c1d07c830b5e145475151600 (git) Affected: 6.6.32 , < 6.6.117 (semver) |
guessed | |
| Linux | Linux |
Affected:
6.8
Unaffected: 0 , < 6.8 (semver) Unaffected: 6.6.117 , ≤ 6.6.* (semver) Unaffected: 6.12.58 , ≤ 6.12.* (semver) Unaffected: 6.17.8 , ≤ 6.17.* (semver) Unaffected: 6.18 , ≤ * (original_commit_for_fix) |
guessed |
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"fs/smb/client/smb2ops.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "939c4e33005e2a56ea8fcedddf0da92df864bd3b",
"status": "affected",
"version": "433042a91f9373241307725b52de573933ffedbf",
"versionType": "git"
},
{
"lessThan": "327f89c21601ebb7889f8c97754b76f08ce95a0c",
"status": "affected",
"version": "4f1fffa2376922f3d1d506e49c0fd445b023a28e",
"versionType": "git"
},
{
"lessThan": "b556c278d43f4707a9073ca74d55581b4f279806",
"status": "affected",
"version": "4f1fffa2376922f3d1d506e49c0fd445b023a28e",
"versionType": "git"
},
{
"lessThan": "5c76f9961c170552c1d07c830b5e145475151600",
"status": "affected",
"version": "4f1fffa2376922f3d1d506e49c0fd445b023a28e",
"versionType": "git"
},
{
"lessThan": "6.6.117",
"status": "affected",
"version": "6.6.32",
"versionType": "semver"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"fs/smb/client/smb2ops.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "6.8"
},
{
"lessThan": "6.8",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.117",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.58",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.17.*",
"status": "unaffected",
"version": "6.17.8",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "6.18",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.117",
"versionStartIncluding": "6.6.32",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.58",
"versionStartIncluding": "6.8",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.17.8",
"versionStartIncluding": "6.8",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.18",
"versionStartIncluding": "6.8",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix potential cfid UAF in smb2_query_info_compound\n\nWhen smb2_query_info_compound() retries, a previously allocated cfid may\nhave been freed in the first attempt.\nBecause cfid wasn\u0027t reset on replay, later cleanup could act on a stale\npointer, leading to a potential use-after-free.\n\nReinitialize cfid to NULL under the replay label.\n\nExample trace (trimmed):\n\nrefcount_t: underflow; use-after-free.\nWARNING: CPU: 1 PID: 11224 at ../lib/refcount.c:28 refcount_warn_saturate+0x9c/0x110\n[...]\nRIP: 0010:refcount_warn_saturate+0x9c/0x110\n[...]\nCall Trace:\n \u003cTASK\u003e\n smb2_query_info_compound+0x29c/0x5c0 [cifs f90b72658819bd21c94769b6a652029a07a7172f]\n ? step_into+0x10d/0x690\n ? __legitimize_path+0x28/0x60\n smb2_queryfs+0x6a/0xf0 [cifs f90b72658819bd21c94769b6a652029a07a7172f]\n smb311_queryfs+0x12d/0x140 [cifs f90b72658819bd21c94769b6a652029a07a7172f]\n ? kmem_cache_alloc+0x18a/0x340\n ? getname_flags+0x46/0x1e0\n cifs_statfs+0x9f/0x2b0 [cifs f90b72658819bd21c94769b6a652029a07a7172f]\n statfs_by_dentry+0x67/0x90\n vfs_statfs+0x16/0xd0\n user_statfs+0x54/0xa0\n __do_sys_statfs+0x20/0x50\n do_syscall_64+0x58/0x80"
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:N - Both halves of the bug are driven entirely by a remote SMB peer \u2014 the server decides when `compound_send_recv()` returns the replayable error (`-EAGAIN`/`-ECONNABORTED`) that reaches `replay_again:`, and it sends the SMB2 lease-break that makes `cached_dir_lease_break()` drop the cfid\u0027s last reference and free it. A malicious/compromised file server or an on-path attacker against an SMB session without signing can reach this over the network or WAN.\nAC:L - The server has deterministic control of every precondition: it triggers the replayable error, times the lease break that frees the cfid, and fails its second CREATE so `open_cached_dir()` returns without resetting `*ret_cfid`, leaving the dangling pointer guaranteed. No memory layout or timing condition outside the attacker\u0027s control is required, and the replay backoff plus a full round trip give a generous heap-grooming window.\nPR:N - The attacker is the remote SMB server or an on-path attacker and holds no privileges or credentials on the victim system. The client-side entry points (`statfs`, `getxattr`, `listxattr`) need only an unprivileged user and in practice fire unprompted from `df`, monitoring agents and container runtimes.\nUI:N - The CIFS mount is a standing deployment condition (fstab/autofs/automount in enterprise and NAS setups), not a per-attempt victim action; once it exists the server drives the entire sequence itself. It only needs to wait for a routine `statfs()`/xattr operation, which recurs continuously without any user acting.\nS:U - The use-after-free corrupts kernel heap memory within the same kernel security authority as the vulnerable cifs client code. No VM, IOMMU, or sandbox boundary is crossed.\nC:H - On replay the stale `cfid-\u003efid.persistent_fid` and `volatile_fid` are read from freed slab memory and transmitted verbatim to the attacker\u0027s server in the SMB2 QUERY_INFO request, a repeatable kernel-heap infoleak usable to defeat KASLR. Controlling the reallocated object escalates this to arbitrary kernel memory disclosure.\nI:H - Reaching `close_cached_dir()` on the dangling pointer runs `list_del(\u0026cfid-\u003eentry)` with attacker-supplied `next`/`prev` (classic unlink arbitrary write), `cfid-\u003ecfids-\u003enum_entries--`, `dput()` on a forged dentry, and `kfree(cfid-\u003epath)` plus an arbitrary-free loop over the dirents list. Together these yield arbitrary write and arbitrary free, sufficient for control-flow hijack and privilege escalation.\nA:H - The reported trace shows `refcount_t: underflow; use-after-free` with a WARNING in `refcount_warn_saturate()` reached from `smb2_query_info_compound()` via `statfs`. Operating on the freed object readily oopses or panics the kernel, and the server can retrigger it at will."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-05T12:09:34.045Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/939c4e33005e2a56ea8fcedddf0da92df864bd3b"
},
{
"url": "https://git.kernel.org/stable/c/327f89c21601ebb7889f8c97754b76f08ce95a0c"
},
{
"url": "https://git.kernel.org/stable/c/b556c278d43f4707a9073ca74d55581b4f279806"
},
{
"url": "https://git.kernel.org/stable/c/5c76f9961c170552c1d07c830b5e145475151600"
}
],
"title": "smb: client: fix potential cfid UAF in smb2_query_info_compound",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2025-40320",
"datePublished": "2025-12-08T00:46:47.670Z",
"dateReserved": "2025-04-16T07:20:57.186Z",
"dateUpdated": "2026-08-05T12:09:34.045Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2025-40320",
"date": "2026-09-16",
"epss": "0.00418",
"percentile": "0.35518"
},
"nvd": "{\"cve\":{\"id\":\"CVE-2025-40320\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-12-08T01:16:04.670\",\"lastModified\":\"2026-07-30T06:24:28.770\",\"vulnStatus\":\"Deferred\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nsmb: client: fix potential cfid UAF in smb2_query_info_compound\\n\\nWhen smb2_query_info_compound() retries, a previously allocated cfid may\\nhave been freed in the first attempt.\\nBecause cfid wasn\u0027t reset on replay, later cleanup could act on a stale\\npointer, leading to a potential use-after-free.\\n\\nReinitialize cfid to NULL under the replay label.\\n\\nExample trace (trimmed):\\n\\nrefcount_t: underflow; use-after-free.\\nWARNING: CPU: 1 PID: 11224 at ../lib/refcount.c:28 refcount_warn_saturate+0x9c/0x110\\n[...]\\nRIP: 0010:refcount_warn_saturate+0x9c/0x110\\n[...]\\nCall Trace:\\n \u003cTASK\u003e\\n smb2_query_info_compound+0x29c/0x5c0 [cifs f90b72658819bd21c94769b6a652029a07a7172f]\\n ? step_into+0x10d/0x690\\n ? __legitimize_path+0x28/0x60\\n smb2_queryfs+0x6a/0xf0 [cifs f90b72658819bd21c94769b6a652029a07a7172f]\\n smb311_queryfs+0x12d/0x140 [cifs f90b72658819bd21c94769b6a652029a07a7172f]\\n ? kmem_cache_alloc+0x18a/0x340\\n ? getname_flags+0x46/0x1e0\\n cifs_statfs+0x9f/0x2b0 [cifs f90b72658819bd21c94769b6a652029a07a7172f]\\n statfs_by_dentry+0x67/0x90\\n vfs_statfs+0x16/0xd0\\n user_statfs+0x54/0xa0\\n __do_sys_statfs+0x20/0x50\\n do_syscall_64+0x58/0x80\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/smb/client/smb2ops.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"433042a91f9373241307725b52de573933ffedbf\",\"lessThan\":\"939c4e33005e2a56ea8fcedddf0da92df864bd3b\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"4f1fffa2376922f3d1d506e49c0fd445b023a28e\",\"lessThan\":\"327f89c21601ebb7889f8c97754b76f08ce95a0c\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"4f1fffa2376922f3d1d506e49c0fd445b023a28e\",\"lessThan\":\"b556c278d43f4707a9073ca74d55581b4f279806\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"4f1fffa2376922f3d1d506e49c0fd445b023a28e\",\"lessThan\":\"5c76f9961c170552c1d07c830b5e145475151600\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"6.6.32\",\"lessThan\":\"6.6.117\",\"versionType\":\"semver\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/smb/client/smb2ops.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"6.8\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"6.8\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.6.117\",\"lessThanOrEqual\":\"6.6.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.58\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.17.8\",\"lessThanOrEqual\":\"6.17.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":9.8,\"baseSeverity\":\"CRITICAL\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":3.9,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/327f89c21601ebb7889f8c97754b76f08ce95a0c\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/5c76f9961c170552c1d07c830b5e145475151600\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/939c4e33005e2a56ea8fcedddf0da92df864bd3b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/b556c278d43f4707a9073ca74d55581b4f279806\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
"redhat_vex": {
"aggregate_severity": "Moderate",
"current_release_date": "2026-07-30T08:37:36+00:00",
"cve": "CVE-2025-40320",
"id": "CVE-2025-40320",
"initial_release_date": "2025-12-08T00:00:00+00:00",
"product_status:fixed": "309",
"product_status:known_affected": "106",
"product_status:known_not_affected": "92",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "kernel: smb: client: fix potential cfid UAF in smb2_query_info_compound",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-40320.json",
"version": "3"
},
"suse_vex": {
"aggregate_severity": "moderate",
"current_release_date": "2026-09-11T01:53:48Z",
"cve": "CVE-2025-40320",
"id": "CVE-2025-40320",
"initial_release_date": "2025-12-09T00:24:09Z",
"product_status:first_fixed": "2",
"product_status:known_affected": "394",
"product_status:known_not_affected": "429",
"product_status:recommended": "384",
"source": "SUSE CSAF VEX",
"status": "interim",
"title": "SUSE CVE CVE-2025-40320",
"url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2025-40320.json",
"version": "33"
}
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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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
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
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.
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.
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