{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "0626e6641f6b467447c81dd7678a69c66f7746cf"
            },
            {
              "fixed": "bf396208418371174869baba9434535cd3288e80"
            },
            {
              "fixed": "7dd0c858e1909769a4c91842724315ee74f1a5f1"
            },
            {
              "fixed": "299db777ea0cfa5c407e41b045c24a14c034c27b"
            },
            {
              "fixed": "99c631d0366c1eab8fb188fe66425f4581ebdde4"
            },
            {
              "fixed": "d6a6aa81eac2c9bff66dc6e191179cb69a14426b"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Linux",
        "name": "Kernel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "5.15.0"
            },
            {
              "fixed": "6.6.141"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.7.0"
            },
            {
              "fixed": "6.12.84"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.13.0"
            },
            {
              "fixed": "6.18.25"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.19.0"
            },
            {
              "fixed": "7.0.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31707.json"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: validate response sizes in ipc_validate_msg()\n\nipc_validate_msg() computes the expected message size for each\nresponse type by adding (or multiplying) attacker-controlled fields\nfrom the daemon response to a fixed struct size in unsigned int\narithmetic.  Three cases can overflow:\n\n  KSMBD_EVENT_RPC_REQUEST:\n      msg_sz = sizeof(struct ksmbd_rpc_command) + resp-\u003epayload_sz;\n  KSMBD_EVENT_SHARE_CONFIG_REQUEST:\n      msg_sz = sizeof(struct ksmbd_share_config_response) +\n               resp-\u003epayload_sz;\n  KSMBD_EVENT_LOGIN_REQUEST_EXT:\n      msg_sz = sizeof(struct ksmbd_login_response_ext) +\n               resp-\u003engroups * sizeof(gid_t);\n\nresp-\u003epayload_sz is __u32 and resp-\u003engroups is __s32.  Each addition\ncan wrap in unsigned int; the multiplication by sizeof(gid_t) mixes\nsigned and size_t, so a negative ngroups is converted to SIZE_MAX\nbefore the multiply.  A wrapped value of msg_sz that happens to\nequal entry-\u003emsg_sz bypasses the size check on the next line, and\ndownstream consumers (smb2pdu.c:6742 memcpy using rpc_resp-\u003epayload_sz,\nkmemdup in ksmbd_alloc_user using resp_ext-\u003engroups) then trust the\nunverified length.\n\nUse check_add_overflow() on the RPC_REQUEST and SHARE_CONFIG_REQUEST\npaths to detect integer overflow without constraining functional\npayload size; userspace ksmbd-tools grows NDR responses in 4096-byte\nchunks for calls like NetShareEnumAll, so a hard transport cap is\nunworkable on the response side.  For LOGIN_REQUEST_EXT, reject\nresp-\u003engroups outside the signed [0, NGROUPS_MAX] range up front and\nreport the error from ipc_validate_msg() so it fires at the IPC\nboundary; with that bound the subsequent multiplication and addition\nstay well below UINT_MAX.  The now-redundant ngroups check and\npr_err in ksmbd_alloc_user() are removed.\n\nThis is the response-side analogue of aab98e2dbd64 (\"ksmbd: fix\ninteger overflows on 32 bit systems\"), which hardened the request\nside.",
  "id": "CVE-2026-31707",
  "modified": "2026-07-15T01:48:58.698057969Z",
  "published": "2026-05-01T13:56:05.219Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/299db777ea0cfa5c407e41b045c24a14c034c27b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/7dd0c858e1909769a4c91842724315ee74f1a5f1"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/99c631d0366c1eab8fb188fe66425f4581ebdde4"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/bf396208418371174869baba9434535cd3288e80"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d6a6aa81eac2c9bff66dc6e191179cb69a14426b"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31707.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-31707"
    },
    {
      "type": "PACKAGE",
      "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
    }
  ],
  "schema_version": "1.8.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "ksmbd: validate response sizes in ipc_validate_msg()"
}