CVE-2026-74631 (GCVE-0-2026-74631)

Vulnerability from cvelistv5 – Published: 2026-08-22 15:32 – Updated: 2026-10-16 19:06
VLAI
Title
net: smc: fix splice entry lifetime imbalance in smc_rx_splice
Summary
In the Linux kernel, the following vulnerability has been resolved: net: smc: fix splice entry lifetime imbalance in smc_rx_splice smc_rx_splice() passes pages to splice_to_pipe() before taking the references that cover the lifetime of each splice entry. In the VM-backed RMB path, splice_to_pipe() may drop unqueued entries through smc_rx_spd_release(), while queued entries are released later via the pipe buffer callback. The old post-splice accounting also derives the number of queued VM pages from an offset mutated while building the descriptor, and a multi-page splice pairs one sock_hold() with multiple sock_put() calls. Take the page and socket references for every candidate entry before splice_to_pipe(), and drop the matching private state, page reference, and socket reference from smc_rx_spd_release() for entries that never get queued. This fixes a refcount imbalance that can underflow page refcounts and trigger a use-after-free.
Severity
8.4 (High)
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-16 19:03 UTC
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 7018 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 9014db202cb764b8e14c53e7bacc81f9a1a2ba7f , < 7ddc7af2ae7fc5a0c0635b245c0824c8b76de5cb (git)
Affected: 9014db202cb764b8e14c53e7bacc81f9a1a2ba7f , < 07ad246529d136d5ef441d5ab4c305d132ff3090 (git)
Affected: 9014db202cb764b8e14c53e7bacc81f9a1a2ba7f , < c841789e456ec6751342fa800639ce8e82ff0e6b (git)
Affected: 9014db202cb764b8e14c53e7bacc81f9a1a2ba7f , < af02c67ce654356c58db20a0bb2db33ace3b07a8 (git)
Affected: 9014db202cb764b8e14c53e7bacc81f9a1a2ba7f , < ca8342b5fc24c249fdb998468f6a168b457c67e5 (git)
Affected: 9014db202cb764b8e14c53e7bacc81f9a1a2ba7f , < 0b7d54cedea5cb158e21925ae0c6c2f5c87ed2a0 (git)
Affected: 9014db202cb764b8e14c53e7bacc81f9a1a2ba7f , < 4515c78f4d9fd577270f012efeb062ea58b3682d (git)
Affected: 9014db202cb764b8e14c53e7bacc81f9a1a2ba7f , < 5d9686af2976741bbd79b150d1c9e60b81e7f12e (git)
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Linux Linux Affected: 4.18
Unaffected: 0 , < 4.18 (semver)
Unaffected: 5.10.266 , ≤ 5.10.* (semver)
Unaffected: 5.15.217 , ≤ 5.15.* (semver)
Unaffected: 6.1.183 , ≤ 6.1.* (semver)
Unaffected: 6.6.152 , ≤ 6.6.* (semver)
Unaffected: 6.12.104 , ≤ 6.12.* (semver)
Unaffected: 6.18.45 , ≤ 6.18.* (semver)
Unaffected: 7.1.9 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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              "value": "AV:L - smc_rx_splice is only reached via splice()/tee() on an SMC socket FD (syscall -\u003e smc_splice_read -\u003e smc_rx_recvmsg with pipe set); remote SMC peers can supply receive-buffer data but cannot execute the vulnerable splice path without a local process invoking splice on that socket.\nAC:L - The attacker controls splice length, can nearly fill the destination pipe to force splice_to_pipe to drop unqueued entries via smc_rx_spd_release, and can hit the multi-page VM-backed RMB path (smcr_buf_type or mixed-buffer vmalloc fallback); no timing race or external victim state is required.\nPR:N - Exploitation requires only completing an SMC session as a network peer to a victim that reads with splice (common zero-copy SMC pattern); no local account, capabilities, or namespace-admin rights on the victim host are needed beyond normal remote connectivity to the SMC service.\nUI:N - No per-exploit victim action is needed beyond an application already using splice on SMC receive; a malicious peer can deliver the receive data while the victim\u0027s normal automated splice path triggers the refcount imbalance without prompts or manual steps.\nS:U - Impact is kernel page refcount underflow and use-after-free within the same kernel security boundary, enabling privilege escalation or crash on the host; it does not cross VM, IOMMU, or sandbox authority boundaries.\nC:H - Refcount imbalance lets smc_rx_spd_release and pipe-buffer teardown free pages while still referenced, creating a UAF on RMB pages that can be turned into arbitrary kernel memory disclosure via heap reuse and spraying.\nI:H - Corrupted page lifetime and dangling pipe_buffer state enable heap metadata corruption and arbitrary kernel writes from the UAF primitive, supporting control-flow hijacking and local privilege escalation.\nA:H - Page refcount underflow and UAF during splice teardown can cause immediate kernel oops/panic; repeated splice from an SMC peer reliably triggers denial-of-service even when full exploitation is not attempted."
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      "cve": "CVE-2026-74631",
      "id": "msrc_CVE-2026-74631",
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      "product_status:fixed": "1",
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      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "net: smc: fix splice entry lifetime imbalance in smc_rx_splice",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-74631.json",
      "version": "4"
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        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: smc: fix splice entry lifetime imbalance in smc_rx_splice\n\nsmc_rx_splice() passes pages to splice_to_pipe() before taking the\nreferences that cover the lifetime of each splice entry. In the\nVM-backed RMB path, splice_to_pipe() may drop unqueued entries through\nsmc_rx_spd_release(), while queued entries are released later via the\npipe buffer callback.\n\nThe old post-splice accounting also derives the number of queued VM pages\nfrom an offset mutated while building the descriptor, and a multi-page\nsplice pairs one sock_hold() with multiple sock_put() calls.\n\nTake the page and socket references for every candidate entry before\nsplice_to_pipe(), and drop the matching private state, page reference,\nand socket reference from smc_rx_spd_release() for entries that never\nget queued. This fixes a refcount imbalance that can underflow page\nrefcounts and trigger a use-after-free."
          },
          {
            "lang": "es",
            "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nnet: smc: corregir el desequilibrio en el tiempo de vida de la entrada de splice en smc_rx_splice\n\nsmc_rx_splice() pasa p\u00e1ginas a splice_to_pipe() antes de tomar las referencias que cubren el tiempo de vida de cada entrada de splice. En la ruta RMB respaldada por VM, splice_to_pipe() puede descartar entradas no encoladas a trav\u00e9s de smc_rx_spd_release(), mientras que las entradas encoladas se liberan m\u00e1s tarde a trav\u00e9s de la devoluci\u00f3n de llamada del b\u00fafer de tuber\u00eda.\n\nLa antigua contabilidad post-splice tambi\u00e9n deriva el n\u00famero de p\u00e1ginas VM encoladas de un desplazamiento mutado mientras se construye el descriptor, y un splice de varias p\u00e1ginas empareja una llamada a sock_hold() con m\u00faltiples llamadas a sock_put().\n\nTomar las referencias de p\u00e1gina y de socket para cada entrada candidata antes de splice_to_pipe(), y descartar el estado privado coincidente, la referencia de p\u00e1gina y la referencia de socket de smc_rx_spd_release() para las entradas que nunca se encolan. Esto corrige un desequilibrio en el contador de referencias que puede causar un desbordamiento negativo en los contadores de referencias de p\u00e1gina y desencadenar un uso despu\u00e9s de liberaci\u00f3n."
          }
        ],
        "id": "CVE-2026-74631",
        "lastModified": "2026-10-16T20:17:48.220",
        "metrics": {
          "cvssMetricV31": [
            {
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                "baseScore": 8.4,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
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                "version": "2.0.3"
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          },
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            "url": "https://git.kernel.org/stable/c/ca8342b5fc24c249fdb998468f6a168b457c67e5"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-10-28T19:44:03+00:00",
      "cve": "CVE-2026-74631",
      "id": "CVE-2026-74631",
      "initial_release_date": "2026-08-22T00:00:00+00:00",
      "product_status:fixed": "320",
      "product_status:known_affected": "157",
      "product_status:known_not_affected": "42",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: net: smc: fix splice entry lifetime imbalance in smc_rx_splice",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74631.json",
      "version": "3"
    },
    "vulnrichment": {
      "containers": {
        "adp": [
          {
            "metrics": [
              {
                "other": {
                  "content": {
                    "id": "CVE-2026-74631",
                    "options": [
                      {
                        "Exploitation": "none"
                      },
                      {
                        "Automatable": "no"
                      },
                      {
                        "Technical Impact": "total"
                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2026-10-16T19:03:01.320271Z",
                    "version": "2.0.3"
                  },
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                }
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2026-10-16T19:03:03.460Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
            {
              "defaultStatus": "unaffected",
              "product": "Linux",
              "programFiles": [
                "net/smc/smc_rx.c"
              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
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              "product": "Linux",
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              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
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                  "version": "4.18"
                },
                {
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                  "status": "unaffected",
                  "version": "0",
                  "versionType": "semver"
                },
                {
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                  "status": "unaffected",
                  "version": "5.10.266",
                  "versionType": "semver"
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                {
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                  "status": "unaffected",
                  "version": "5.15.217",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.1.*",
                  "status": "unaffected",
                  "version": "6.1.183",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.6.*",
                  "status": "unaffected",
                  "version": "6.6.152",
                  "versionType": "semver"
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                {
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                  "status": "unaffected",
                  "version": "6.18.45",
                  "versionType": "semver"
                },
                {
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                  "status": "unaffected",
                  "version": "7.1.9",
                  "versionType": "semver"
                },
                {
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                  "status": "unaffected",
                  "version": "7.2",
                  "versionType": "original_commit_for_fix"
                }
              ]
            }
          ],
          "cpeApplicability": [
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                      "versionEndExcluding": "5.10.266",
                      "versionStartIncluding": "4.18",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "5.15.217",
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                      "vulnerable": true
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                  "negate": false,
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          ],
          "descriptions": [
            {
              "lang": "en",
              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: smc: fix splice entry lifetime imbalance in smc_rx_splice\n\nsmc_rx_splice() passes pages to splice_to_pipe() before taking the\nreferences that cover the lifetime of each splice entry. In the\nVM-backed RMB path, splice_to_pipe() may drop unqueued entries through\nsmc_rx_spd_release(), while queued entries are released later via the\npipe buffer callback.\n\nThe old post-splice accounting also derives the number of queued VM pages\nfrom an offset mutated while building the descriptor, and a multi-page\nsplice pairs one sock_hold() with multiple sock_put() calls.\n\nTake the page and socket references for every candidate entry before\nsplice_to_pipe(), and drop the matching private state, page reference,\nand socket reference from smc_rx_spd_release() for entries that never\nget queued. This fixes a refcount imbalance that can underflow page\nrefcounts and trigger a use-after-free."
            }
          ],
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                "baseSeverity": "HIGH",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "scenarios": [
                {
                  "lang": "en",
                  "value": "AV:L - smc_rx_splice is only reached via splice()/tee() on an SMC socket FD (syscall -\u003e smc_splice_read -\u003e smc_rx_recvmsg with pipe set); remote SMC peers can supply receive-buffer data but cannot execute the vulnerable splice path without a local process invoking splice on that socket.\nAC:L - The attacker controls splice length, can nearly fill the destination pipe to force splice_to_pipe to drop unqueued entries via smc_rx_spd_release, and can hit the multi-page VM-backed RMB path (smcr_buf_type or mixed-buffer vmalloc fallback); no timing race or external victim state is required.\nPR:N - Exploitation requires only completing an SMC session as a network peer to a victim that reads with splice (common zero-copy SMC pattern); no local account, capabilities, or namespace-admin rights on the victim host are needed beyond normal remote connectivity to the SMC service.\nUI:N - No per-exploit victim action is needed beyond an application already using splice on SMC receive; a malicious peer can deliver the receive data while the victim\u0027s normal automated splice path triggers the refcount imbalance without prompts or manual steps.\nS:U - Impact is kernel page refcount underflow and use-after-free within the same kernel security boundary, enabling privilege escalation or crash on the host; it does not cross VM, IOMMU, or sandbox authority boundaries.\nC:H - Refcount imbalance lets smc_rx_spd_release and pipe-buffer teardown free pages while still referenced, creating a UAF on RMB pages that can be turned into arbitrary kernel memory disclosure via heap reuse and spraying.\nI:H - Corrupted page lifetime and dangling pipe_buffer state enable heap metadata corruption and arbitrary kernel writes from the UAF primitive, supporting control-flow hijacking and local privilege escalation.\nA:H - Page refcount underflow and UAF during splice teardown can cause immediate kernel oops/panic; repeated splice from an SMC peer reliably triggers denial-of-service even when full exploitation is not attempted."
                }
              ]
            }
          ],
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            "dateUpdated": "2026-08-25T05:40:55.722Z",
            "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "shortName": "Linux"
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            },
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              "url": "https://git.kernel.org/stable/c/4515c78f4d9fd577270f012efeb062ea58b3682d"
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            {
              "url": "https://git.kernel.org/stable/c/5d9686af2976741bbd79b150d1c9e60b81e7f12e"
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          "title": "net: smc: fix splice entry lifetime imbalance in smc_rx_splice",
          "x_generator": {
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      "cveMetadata": {
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "assignerShortName": "Linux",
        "cveId": "CVE-2026-74631",
        "datePublished": "2026-08-22T15:32:12.334Z",
        "dateReserved": "2026-08-15T05:44:03.922Z",
        "dateUpdated": "2026-10-16T19:06:03.774Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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