CVE-2026-98173 (GCVE-0-2026-98173)
Vulnerability from cvelistv5
Published
2026-10-06 08:44
Modified
2026-10-21 12:54
Severity ?
7.5 (High) - CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: smb: client: fix use-after-free of iface in cifs_try_adding_channels() cifs_try_adding_channels() iterates ses->iface_list with list_for_each_entry_safe_from(), which captures the next entry (niface) under iface_lock. The loop body then drops iface_lock for the whole duration of cifs_ses_add_channel(). A concurrent interface refresh (SMB3_request_interfaces() -> parse_server_interfaces()) marks all ifaces inactive and removes and frees any that are not re-advertised via list_del() + kref_put(), where release_iface() is a bare kfree(). Since niface typically has no channel holding a reference, the list reference is its last and it can be freed inside the unlocked window. On continue, the iterator advance step then dereferences niface->iface_head.next, and the loop body reads iface->rdma_capable/is_active, both on freed memory. Fix this by never keeping an unreferenced list pointer across the unlocked window. Each channel attempt now re-scans the list from the head under iface_lock, takes a kref on the selected candidate, and passes only that referenced candidate to cifs_ses_add_channel(). weight_fulfilled still tracks selection progress, so restarting the scan preserves the original weighted distribution and the weight_fulfilled-before-kref_put ordering on the failure path. Add a per-pass attempts cap so a flapping interface refresh cannot keep the inner loop spinning within a single tries increment.
References
Impacted products
Vendor Product Version
Linux Linux Version: aa45dadd34e44fcd6a9df4b395bee5b5633b4cec
Version: aa45dadd34e44fcd6a9df4b395bee5b5633b4cec
Version: aa45dadd34e44fcd6a9df4b395bee5b5633b4cec
Version: aa45dadd34e44fcd6a9df4b395bee5b5633b4cec
Version: aa45dadd34e44fcd6a9df4b395bee5b5633b4cec
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          "programFiles": [
            "fs/smb/client/sess.c"
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      "cpeApplicability": [
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix use-after-free of iface in cifs_try_adding_channels()\n\ncifs_try_adding_channels() iterates ses-\u003eiface_list with\nlist_for_each_entry_safe_from(), which captures the next entry\n(niface) under iface_lock.  The loop body then drops iface_lock for\nthe whole duration of cifs_ses_add_channel().\n\nA concurrent interface refresh (SMB3_request_interfaces() -\u003e\nparse_server_interfaces()) marks all ifaces inactive and removes and\nfrees any that are not re-advertised via list_del() + kref_put(),\nwhere release_iface() is a bare kfree().  Since niface typically has\nno channel holding a reference, the list reference is its last and it\ncan be freed inside the unlocked window.  On continue, the iterator\nadvance step then dereferences niface-\u003eiface_head.next, and the loop\nbody reads iface-\u003erdma_capable/is_active, both on freed memory.\n\nFix this by never keeping an unreferenced list pointer across the\nunlocked window.  Each channel attempt now re-scans the list from the\nhead under iface_lock, takes a kref on the selected candidate, and\npasses only that referenced candidate to cifs_ses_add_channel().\nweight_fulfilled still tracks selection progress, so restarting the\nscan preserves the original weighted distribution and the\nweight_fulfilled-before-kref_put ordering on the failure path.\n\nAdd a per-pass attempts cap so a flapping interface refresh cannot\nkeep the inner loop spinning within a single tries increment."
        }
      ],
      "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 - A malicious SMB server sends the bad data over TCP/445 in its FSCTL_QUERY_NETWORK_INTERFACE_INFO responses. A later response leaves out an interface, so parse_server_interfaces() does list_del() and kref_put() and frees it. cifs_try_adding_channels() still holds niface after dropping iface_lock for cifs_ses_add_channel(), and that pointer now refers to freed memory.\nAC:H - Multichannel is off by default (multichannel=false, max_channels=1), so the victim must mount with multichannel or max_channels\u003e1. The server also has to line up a refresh from the 600s smb2_query_server_interfaces worker with the unlocked add-channel window. It can stall channel setup and force reconnects to retry, but it does not schedule the worker.\nPR:N - The attacker only runs a rogue SMB server and needs no account or privilege on the victim client. The interface list is server-supplied data the client trusts during the session it opened.\nUI:R - A victim or admin has to mount a share from the attacker\u0027s server with multichannel turned on. CIFS mounts are not FS_USERNS_MOUNT, so the attacker cannot set up the client side alone.\nS:U - The memory corruption stays inside the client kernel\u0027s own security authority. No VM or other trust boundary is crossed.\nC:H - The loop continues through freed niface-\u003eiface_head.next and reads iface-\u003erdma_capable, is_active, speed and sockaddr from the freed cifs_server_iface. The attacker can refill that heap object with their own data, which lets the kernel follow attacker-chosen pointers.\nI:H - Once the freed entry is reallocated, the loop does kref_get() and weight_fulfilled++/num_channels++ through the stale or forged iface pointer. That is a kernel write at a location the attacker influences, and cifs_ses_add_channel() then uses the forged object.\nA:H - Dereferencing the freed list entry in cifs_try_adding_channels() can oops or panic the client. The server can force reconnects to re-enter this path repeatedly."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-21T12:54:49.437Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/ee0d8f83d68f6e6509f092c997ccab3c8c801538"
        },
        {
          "url": "https://git.kernel.org/stable/c/c941f1ebfd26f683de81091473f3596a218abff0"
        },
        {
          "url": "https://git.kernel.org/stable/c/e99040e5e9c60441e6b4725e1a7b88c3106ae903"
        },
        {
          "url": "https://git.kernel.org/stable/c/ec36b38e65596950e6c29bed7dfc90b98707c19c"
        },
        {
          "url": "https://git.kernel.org/stable/c/d034e836eefd7ce75e588f7031cffbeec594f5ac"
        }
      ],
      "title": "smb: client: fix use-after-free of iface in cifs_try_adding_channels()",
      "x_generator": {
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  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98173",
    "datePublished": "2026-10-06T08:44:17.567Z",
    "dateReserved": "2026-09-25T10:25:14.322Z",
    "dateUpdated": "2026-10-21T12:54:49.437Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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