CVE-2026-31707 (GCVE-0-2026-31707)

Vulnerability from cvelistv5 – Published: 2026-05-01 13:56 – Updated: 2026-05-11 22:14
VLAI?
Title
ksmbd: validate response sizes in ipc_validate_msg()
Summary
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) + resp->payload_sz; KSMBD_EVENT_SHARE_CONFIG_REQUEST: msg_sz = sizeof(struct ksmbd_share_config_response) + resp->payload_sz; KSMBD_EVENT_LOGIN_REQUEST_EXT: msg_sz = sizeof(struct ksmbd_login_response_ext) + resp->ngroups * sizeof(gid_t); resp->payload_sz is __u32 and resp->ngroups 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->msg_sz bypasses the size check on the next line, and downstream consumers (smb2pdu.c:6742 memcpy using rpc_resp->payload_sz, kmemdup in ksmbd_alloc_user using resp_ext->ngroups) 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->ngroups 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 ("ksmbd: fix integer overflows on 32 bit systems"), which hardened the request side.
Severity ?
7.1 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 0626e6641f6b467447c81dd7678a69c66f7746cf , < 7dd0c858e1909769a4c91842724315ee74f1a5f1 (git)
Affected: 0626e6641f6b467447c81dd7678a69c66f7746cf , < 299db777ea0cfa5c407e41b045c24a14c034c27b (git)
Affected: 0626e6641f6b467447c81dd7678a69c66f7746cf , < 99c631d0366c1eab8fb188fe66425f4581ebdde4 (git)
Affected: 0626e6641f6b467447c81dd7678a69c66f7746cf , < d6a6aa81eac2c9bff66dc6e191179cb69a14426b (git)
Create a notification for this product.
Linux Linux Affected: 5.15
Unaffected: 0 , < 5.15 (semver)
Unaffected: 6.12.84 , ≤ 6.12.* (semver)
Unaffected: 6.18.25 , ≤ 6.18.* (semver)
Unaffected: 7.0.2 , ≤ 7.0.* (semver)
Unaffected: 7.1-rc1 , ≤ * (original_commit_for_fix)
Create a notification for this product.
Show details on NVD website
To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/mgmt/user_config.c",
            "fs/smb/server/transport_ipc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "7dd0c858e1909769a4c91842724315ee74f1a5f1",
              "status": "affected",
              "version": "0626e6641f6b467447c81dd7678a69c66f7746cf",
              "versionType": "git"
            },
            {
              "lessThan": "299db777ea0cfa5c407e41b045c24a14c034c27b",
              "status": "affected",
              "version": "0626e6641f6b467447c81dd7678a69c66f7746cf",
              "versionType": "git"
            },
            {
              "lessThan": "99c631d0366c1eab8fb188fe66425f4581ebdde4",
              "status": "affected",
              "version": "0626e6641f6b467447c81dd7678a69c66f7746cf",
              "versionType": "git"
            },
            {
              "lessThan": "d6a6aa81eac2c9bff66dc6e191179cb69a14426b",
              "status": "affected",
              "version": "0626e6641f6b467447c81dd7678a69c66f7746cf",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/mgmt/user_config.c",
            "fs/smb/server/transport_ipc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.15"
            },
            {
              "lessThan": "5.15",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.84",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.25",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.2",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.84",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.25",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.0.2",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1-rc1",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "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."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
            "version": "3.1"
          }
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-11T22:14:12.107Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/7dd0c858e1909769a4c91842724315ee74f1a5f1"
        },
        {
          "url": "https://git.kernel.org/stable/c/299db777ea0cfa5c407e41b045c24a14c034c27b"
        },
        {
          "url": "https://git.kernel.org/stable/c/99c631d0366c1eab8fb188fe66425f4581ebdde4"
        },
        {
          "url": "https://git.kernel.org/stable/c/d6a6aa81eac2c9bff66dc6e191179cb69a14426b"
        }
      ],
      "title": "ksmbd: validate response sizes in ipc_validate_msg()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31707",
    "datePublished": "2026-05-01T13:56:05.219Z",
    "dateReserved": "2026-03-09T15:48:24.132Z",
    "dateUpdated": "2026-05-11T22:14:12.107Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-31707",
      "date": "2026-05-21",
      "epss": "0.00013",
      "percentile": "0.02389"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-31707\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-05-01T14:16:20.720\",\"lastModified\":\"2026-05-06T20:26:38.560\",\"vulnStatus\":\"Analyzed\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"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.\"}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H\",\"baseScore\":7.1,\"baseSeverity\":\"HIGH\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.2}]},\"weaknesses\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-787\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"5.15\",\"versionEndExcluding\":\"6.12.84\",\"matchCriteriaId\":\"04651641-C387-4546-B02F-17BA989CC253\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.13\",\"versionEndExcluding\":\"6.18.25\",\"matchCriteriaId\":\"8B0A7E0E-F6D8-45DB-8CD9-01839FE40A6C\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.19\",\"versionEndExcluding\":\"7.0.2\",\"matchCriteriaId\":\"1BD58F1E-7C20-4C0D-92A2-FAC5CBFBE8A8\"}]}]}],\"references\":[{\"url\":\"https://git.kernel.org/stable/c/299db777ea0cfa5c407e41b045c24a14c034c27b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/7dd0c858e1909769a4c91842724315ee74f1a5f1\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/99c631d0366c1eab8fb188fe66425f4581ebdde4\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/d6a6aa81eac2c9bff66dc6e191179cb69a14426b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]}]}}"
  }
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




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

Author Source Type Date Other

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.