{
  "cveId": "CVE-2026-31707",
  "url": "https://patchblox.com/security/cve/CVE-2026-31707",
  "summary": "CVE-2026-31707 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-31707, released May 15, 2026. It is not reported as exploited. Patch Radar priority: High.",
  "title": "ksmbd: validate response sizes in ipc_validate_msg()",
  "description": "In the Linux kernel, the following vulnerability has been resolved:  ksmbd: validate response sizes in ipc_validate_msg()  ipc_validate_msg() computes the expected message size for each response type by adding (or multiplying) attacker-controlled fields from the daemon response to a fixed struct size in unsigned int arithmetic.  Three cases can overflow:    KSMBD_EVENT_RPC_REQUEST:       msg_sz = sizeof(struct ksmbd_rpc_command) \u002B resp-\u003Epayload_sz;   KSMBD_EVENT_SHARE_CONFIG_REQUEST:       msg_sz = sizeof(struct ksmbd_share_config_response) \u002B                resp-\u003Epayload_sz;   KSMBD_EVENT_LOGIN_REQUEST_EXT:       msg_sz = sizeof(struct ksmbd_login_response_ext) \u002B                resp-\u003Engroups * sizeof(gid_t);  resp-\u003Epayload_sz is __u32 and resp-\u003Engroups is __s32.  Each addition can wrap in unsigned int; the multiplication by sizeof(gid_t) mixes signed and size_t, so a negative ngroups is converted to SIZE_MAX before the multiply.  A wrapped value of msg_sz that happens to equal entry-\u003Emsg_sz bypasses the size check on the next line, and downstream consumers (smb2pdu.c:6742 memcpy using rpc_resp-\u003Epayload_sz, kmemdup in ksmbd_alloc_user using resp_ext-\u003Engroups) then trust the unverified length.  Use check_add_overflow() on the RPC_REQUEST and SHARE_CONFIG_REQUEST paths to detect integer overflow without constraining functional payload size; userspace ksmbd-tools grows NDR responses in 4096-byte chunks for calls like NetShareEnumAll, so a hard transport cap is unworkable on the response side.  For LOGIN_REQUEST_EXT, reject resp-\u003Engroups outside the signed [0, NGROUPS_MAX] range up front and report the error from ipc_validate_msg() so it fires at the IPC boundary; with that bound the subsequent multiplication and addition stay well below UINT_MAX.  The now-redundant ngroups check and pr_err in ksmbd_alloc_user() are removed.  This is the response-side analogue of aab98e2dbd64 (\u0022ksmbd: fix integer overflows on 32 bit systems\u0022), which hardened the request side.",
  "published": "2026-05-01T14:16:20Z",
  "severity": "Important",
  "cvss": 7.1,
  "cvssVector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
  "epss": 0.00125,
  "epssPercentile": 0.02255,
  "priority": "High",
  "priorityTier": 3,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "vendorAdvisory": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-31707",
  "fixes": [
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 13.5 (trixie)",
      "fixedVersion": "6.12.85-1",
      "fix": "DEBIAN-CVE-2026-31707",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-31707",
      "released": "2026-05-15T16:01:09Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "7.0.3-1",
      "fix": "DEBIAN-CVE-2026-31707",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-31707",
      "released": "2026-05-15T16:01:09Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T13:06:02Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}