CVE-2025-40320 (GCVE-0-2025-40320)

Vulnerability from cvelistv5 – Published: 2025-12-08 00:46 – Updated: 2026-08-05 12:09
VLAI
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)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version
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)
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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)
Create a notification for this product.
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{
  "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": [
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              "status": "affected",
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          "vendor": "Linux",
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              "status": "unaffected",
              "version": "6.6.117",
              "versionType": "semver"
            },
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              "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",
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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: 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."
            }
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        }
      ],
      "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",
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        "engine": "bippy-1.2.0"
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  },
  "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": "2026-08-07",
      "epss": "0.00409",
      "percentile": "0.33642"
    },
    "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"
    }
  }
}



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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

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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.


Detection rules are retrieved from Rulezet.