CVE-2026-43215 (GCVE-0-2026-43215)
Vulnerability from cvelistv5
Published
2026-05-06 11:28
Modified
2026-08-05 12:26
Severity ?
8.8 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: cifs: Fix locking usage for tcon fields We used to use the cifs_tcp_ses_lock to protect a lot of objects that are not just the server, ses or tcon lists. We later introduced srv_lock, ses_lock and tc_lock to protect fields within the corresponding structs. This was done to provide a more granular protection and avoid unnecessary serialization. There were still a couple of uses of cifs_tcp_ses_lock to provide tcon fields. In this patch, I've replaced them with tc_lock.
References
Impacted products
Vendor Product Version
Linux Linux Version: d7d7a66aacd6fd8ca57baf08a7bac5421282f6f8
Version: d7d7a66aacd6fd8ca57baf08a7bac5421282f6f8
Version: d7d7a66aacd6fd8ca57baf08a7bac5421282f6f8
Version: d7d7a66aacd6fd8ca57baf08a7bac5421282f6f8
Version: d7d7a66aacd6fd8ca57baf08a7bac5421282f6f8
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/client/cached_dir.c",
            "fs/smb/client/smb2misc.c",
            "fs/smb/client/smb2ops.c",
            "fs/smb/client/smb2pdu.c",
            "fs/smb/client/trace.h"
          ],
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            "fs/smb/client/smb2misc.c",
            "fs/smb/client/smb2ops.c",
            "fs/smb/client/smb2pdu.c",
            "fs/smb/client/trace.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "version": "6.0"
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              "version": "0",
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              "status": "unaffected",
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              "status": "unaffected",
              "version": "6.12.75",
              "versionType": "semver"
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            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.16",
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              "lessThanOrEqual": "6.19.*",
              "status": "unaffected",
              "version": "6.19.6",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.0",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.128",
                  "versionStartIncluding": "6.0",
                  "vulnerable": true
                },
                {
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                  "versionEndExcluding": "6.12.75",
                  "versionStartIncluding": "6.0",
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              "negate": false,
              "operator": "OR"
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          ]
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncifs: Fix locking usage for tcon fields\n\nWe used to use the cifs_tcp_ses_lock to protect a lot of objects\nthat are not just the server, ses or tcon lists. We later introduced\nsrv_lock, ses_lock and tc_lock to protect fields within the\ncorresponding structs. This was done to provide a more granular\nprotection and avoid unnecessary serialization.\n\nThere were still a couple of uses of cifs_tcp_ses_lock to provide\ntcon fields. In this patch, I\u0027ve replaced them with tc_lock."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The vulnerable CIFS/SMB client code is exercised through SMB protocol activity with a remote server, including DFS referral handling, reconnects, cancelled closes, and cached directory lease cleanup. A malicious or compromised SMB server can influence these network-driven paths after a client connects.\nAC:L - The issue is a locking/refcount race, but the remote SMB peer can repeatedly trigger reconnects, delayed/cancelled responses, DFS behavior, and lease/cached-directory activity to exercise the affected paths. There is no rare configuration or uncontrollable one-shot condition required beyond a CIFS mount being in use.\nPR:N - The attacker does not need privileges on the vulnerable client system; they can act as the SMB server or network peer providing crafted behavior to the CIFS client. Although mounting CIFS locally is privileged, that is victim-side setup/user interaction rather than attacker privileges on the impacted host.\nUI:R - Exploitation requires the client system to mount or otherwise use an SMB/CIFS share, which is a victim/user or administrator action. Once connected, the malicious server can drive the vulnerable network paths.\nS:U - The impact is within the same Linux kernel security authority running the CIFS client. This is standard kernel memory corruption/panic potential, not a VM escape or cross-authority boundary bypass.\nC:H - The inconsistent locking can corrupt the tcon reference count and allow use-after-free of `struct cifs_tcon`. Kernel UAF conditions are reasonably capable of being shaped into memory disclosure primitives.\nI:H - The same premature free and later dereference/use of the tcon object creates kernel heap use-after-free memory corruption. Under the required higher-severity rule, this is treated as potentially exploitable for arbitrary write or control-flow compromise.\nA:H - At minimum, refcount corruption and use-after-free of a live CIFS tcon can lead to kernel oops, panic, or hangs in reconnect/close/DFS workqueue paths. The condition can be triggered repeatedly by malicious SMB server behavior while the share is mounted."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:26:40.744Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/953953abb66e52c224057ab91e404284fefeab62"
        },
        {
          "url": "https://git.kernel.org/stable/c/601dd3b79769b38d30b693c40afdb2a4b7edf9d0"
        },
        {
          "url": "https://git.kernel.org/stable/c/3969db6b22e3d90d8c5f22ac1a7fe0350a94c136"
        },
        {
          "url": "https://git.kernel.org/stable/c/8c59eeeeffa1524ef57e173a89a1a3ff539888d5"
        },
        {
          "url": "https://git.kernel.org/stable/c/96c4af418586ee9a6aab61738644366426e05316"
        }
      ],
      "title": "cifs: Fix locking usage for tcon fields",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-43215",
    "datePublished": "2026-05-06T11:28:17.425Z",
    "dateReserved": "2026-05-01T14:12:55.993Z",
    "dateUpdated": "2026-08-05T12:26:40.744Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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