CVE-2026-31669 (GCVE-0-2026-31669)

Vulnerability from cvelistv5 – Published: 2026-04-24 14:45 – Updated: 2026-05-11 22:13
VLAI
Title
mptcp: fix slab-use-after-free in __inet_lookup_established
Summary
In the Linux kernel, the following vulnerability has been resolved: mptcp: fix slab-use-after-free in __inet_lookup_established The ehash table lookups are lockless and rely on SLAB_TYPESAFE_BY_RCU to guarantee socket memory stability during RCU read-side critical sections. Both tcp_prot and tcpv6_prot have their slab caches created with this flag via proto_register(). However, MPTCP's mptcp_subflow_init() copies tcpv6_prot into tcpv6_prot_override during inet_init() (fs_initcall, level 5), before inet6_init() (module_init/device_initcall, level 6) has called proto_register(&tcpv6_prot). At that point, tcpv6_prot.slab is still NULL, so tcpv6_prot_override.slab remains NULL permanently. This causes MPTCP v6 subflow child sockets to be allocated via kmalloc (falling into kmalloc-4k) instead of the TCPv6 slab cache. The kmalloc-4k cache lacks SLAB_TYPESAFE_BY_RCU, so when these sockets are freed without SOCK_RCU_FREE (which is cleared for child sockets by design), the memory can be immediately reused. Concurrent ehash lookups under rcu_read_lock can then access freed memory, triggering a slab-use-after-free in __inet_lookup_established. Fix this by splitting the IPv6-specific initialization out of mptcp_subflow_init() into a new mptcp_subflow_v6_init(), called from mptcp_proto_v6_init() before protocol registration. This ensures tcpv6_prot_override.slab correctly inherits the SLAB_TYPESAFE_BY_RCU slab cache.
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: b19bc2945b40b9fd38e835700907ffe8534ef0de , < f6e1f25fa5e733570f6d6fe37a4dfed2a0deba47 (git)
Affected: b19bc2945b40b9fd38e835700907ffe8534ef0de , < fb1f54b7d16f393b8b65d328410f78b4beea8fcc (git)
Affected: b19bc2945b40b9fd38e835700907ffe8534ef0de , < 3fd6547f5b8ac99687be6d937a0321efda760597 (git)
Affected: b19bc2945b40b9fd38e835700907ffe8534ef0de , < eb9c6aeb512f877cf397deb1e4526f646c70e4a7 (git)
Affected: b19bc2945b40b9fd38e835700907ffe8534ef0de , < 15fa9ead4d5e6b6b9c794e84144146c917f2cb62 (git)
Affected: b19bc2945b40b9fd38e835700907ffe8534ef0de , < b313e9037d98c13938740e5ebda7852929366dff (git)
Affected: b19bc2945b40b9fd38e835700907ffe8534ef0de , < 9b55b253907e7431210483519c5ad711a37dafa1 (git)
Create a notification for this product.
Linux Linux Affected: 5.12
Unaffected: 0 , < 5.12 (semver)
Unaffected: 5.15.203 , ≤ 5.15.* (semver)
Unaffected: 6.1.169 , ≤ 6.1.* (semver)
Unaffected: 6.6.135 , ≤ 6.6.* (semver)
Unaffected: 6.12.82 , ≤ 6.12.* (semver)
Unaffected: 6.18.23 , ≤ 6.18.* (semver)
Unaffected: 6.19.13 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (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": [
            "net/mptcp/protocol.c",
            "net/mptcp/protocol.h",
            "net/mptcp/subflow.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "f6e1f25fa5e733570f6d6fe37a4dfed2a0deba47",
              "status": "affected",
              "version": "b19bc2945b40b9fd38e835700907ffe8534ef0de",
              "versionType": "git"
            },
            {
              "lessThan": "fb1f54b7d16f393b8b65d328410f78b4beea8fcc",
              "status": "affected",
              "version": "b19bc2945b40b9fd38e835700907ffe8534ef0de",
              "versionType": "git"
            },
            {
              "lessThan": "3fd6547f5b8ac99687be6d937a0321efda760597",
              "status": "affected",
              "version": "b19bc2945b40b9fd38e835700907ffe8534ef0de",
              "versionType": "git"
            },
            {
              "lessThan": "eb9c6aeb512f877cf397deb1e4526f646c70e4a7",
              "status": "affected",
              "version": "b19bc2945b40b9fd38e835700907ffe8534ef0de",
              "versionType": "git"
            },
            {
              "lessThan": "15fa9ead4d5e6b6b9c794e84144146c917f2cb62",
              "status": "affected",
              "version": "b19bc2945b40b9fd38e835700907ffe8534ef0de",
              "versionType": "git"
            },
            {
              "lessThan": "b313e9037d98c13938740e5ebda7852929366dff",
              "status": "affected",
              "version": "b19bc2945b40b9fd38e835700907ffe8534ef0de",
              "versionType": "git"
            },
            {
              "lessThan": "9b55b253907e7431210483519c5ad711a37dafa1",
              "status": "affected",
              "version": "b19bc2945b40b9fd38e835700907ffe8534ef0de",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/mptcp/protocol.c",
            "net/mptcp/protocol.h",
            "net/mptcp/subflow.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.12"
            },
            {
              "lessThan": "5.12",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.203",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.169",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.135",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.82",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.23",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.19.*",
              "status": "unaffected",
              "version": "6.19.13",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.0",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.203",
                  "versionStartIncluding": "5.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.169",
                  "versionStartIncluding": "5.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.135",
                  "versionStartIncluding": "5.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.82",
                  "versionStartIncluding": "5.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.23",
                  "versionStartIncluding": "5.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.19.13",
                  "versionStartIncluding": "5.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.0",
                  "versionStartIncluding": "5.12",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmptcp: fix slab-use-after-free in __inet_lookup_established\n\nThe ehash table lookups are lockless and rely on\nSLAB_TYPESAFE_BY_RCU to guarantee socket memory stability\nduring RCU read-side critical sections. Both tcp_prot and\ntcpv6_prot have their slab caches created with this flag\nvia proto_register().\n\nHowever, MPTCP\u0027s mptcp_subflow_init() copies tcpv6_prot into\ntcpv6_prot_override during inet_init() (fs_initcall, level 5),\nbefore inet6_init() (module_init/device_initcall, level 6) has\ncalled proto_register(\u0026tcpv6_prot). At that point,\ntcpv6_prot.slab is still NULL, so tcpv6_prot_override.slab\nremains NULL permanently.\n\nThis causes MPTCP v6 subflow child sockets to be allocated via\nkmalloc (falling into kmalloc-4k) instead of the TCPv6 slab\ncache. The kmalloc-4k cache lacks SLAB_TYPESAFE_BY_RCU, so\nwhen these sockets are freed without SOCK_RCU_FREE (which is\ncleared for child sockets by design), the memory can be\nimmediately reused. Concurrent ehash lookups under\nrcu_read_lock can then access freed memory, triggering a\nslab-use-after-free in __inet_lookup_established.\n\nFix this by splitting the IPv6-specific initialization out of\nmptcp_subflow_init() into a new mptcp_subflow_v6_init(), called\nfrom mptcp_proto_v6_init() before protocol registration. This\nensures tcpv6_prot_override.slab correctly inherits the\nSLAB_TYPESAFE_BY_RCU slab cache."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          }
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-11T22:13:21.124Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/f6e1f25fa5e733570f6d6fe37a4dfed2a0deba47"
        },
        {
          "url": "https://git.kernel.org/stable/c/fb1f54b7d16f393b8b65d328410f78b4beea8fcc"
        },
        {
          "url": "https://git.kernel.org/stable/c/3fd6547f5b8ac99687be6d937a0321efda760597"
        },
        {
          "url": "https://git.kernel.org/stable/c/eb9c6aeb512f877cf397deb1e4526f646c70e4a7"
        },
        {
          "url": "https://git.kernel.org/stable/c/15fa9ead4d5e6b6b9c794e84144146c917f2cb62"
        },
        {
          "url": "https://git.kernel.org/stable/c/b313e9037d98c13938740e5ebda7852929366dff"
        },
        {
          "url": "https://git.kernel.org/stable/c/9b55b253907e7431210483519c5ad711a37dafa1"
        }
      ],
      "title": "mptcp: fix slab-use-after-free in __inet_lookup_established",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31669",
    "datePublished": "2026-04-24T14:45:17.295Z",
    "dateReserved": "2026-03-09T15:48:24.130Z",
    "dateUpdated": "2026-05-11T22:13:21.124Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-31669",
      "date": "2026-06-19",
      "epss": "0.004",
      "percentile": "0.31687"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-31669\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-04-24T15:16:46.663\",\"lastModified\":\"2026-04-27T20:09:25.553\",\"vulnStatus\":\"Analyzed\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nmptcp: fix slab-use-after-free in __inet_lookup_established\\n\\nThe ehash table lookups are lockless and rely on\\nSLAB_TYPESAFE_BY_RCU to guarantee socket memory stability\\nduring RCU read-side critical sections. Both tcp_prot and\\ntcpv6_prot have their slab caches created with this flag\\nvia proto_register().\\n\\nHowever, MPTCP\u0027s mptcp_subflow_init() copies tcpv6_prot into\\ntcpv6_prot_override during inet_init() (fs_initcall, level 5),\\nbefore inet6_init() (module_init/device_initcall, level 6) has\\ncalled proto_register(\u0026tcpv6_prot). At that point,\\ntcpv6_prot.slab is still NULL, so tcpv6_prot_override.slab\\nremains NULL permanently.\\n\\nThis causes MPTCP v6 subflow child sockets to be allocated via\\nkmalloc (falling into kmalloc-4k) instead of the TCPv6 slab\\ncache. The kmalloc-4k cache lacks SLAB_TYPESAFE_BY_RCU, so\\nwhen these sockets are freed without SOCK_RCU_FREE (which is\\ncleared for child sockets by design), the memory can be\\nimmediately reused. Concurrent ehash lookups under\\nrcu_read_lock can then access freed memory, triggering a\\nslab-use-after-free in __inet_lookup_established.\\n\\nFix this by splitting the IPv6-specific initialization out of\\nmptcp_subflow_init() into a new mptcp_subflow_v6_init(), called\\nfrom mptcp_proto_v6_init() before protocol registration. This\\nensures tcpv6_prot_override.slab correctly inherits the\\nSLAB_TYPESAFE_BY_RCU slab cache.\"}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":9.8,\"baseSeverity\":\"CRITICAL\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":3.9,\"impactScore\":5.9}]},\"weaknesses\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-416\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"5.12.1\",\"versionEndExcluding\":\"5.15.203\",\"matchCriteriaId\":\"AA3D6441-4F2E-41AB-A26D-388B03A5932F\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"5.16\",\"versionEndExcluding\":\"6.1.169\",\"matchCriteriaId\":\"DBEC0E5D-641C-4E98-A6D9-5799B10CE451\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.2\",\"versionEndExcluding\":\"6.6.135\",\"matchCriteriaId\":\"15C1A1B2-14EE-494C-AF3E-D5A7BA640B39\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.7\",\"versionEndExcluding\":\"6.12.82\",\"matchCriteriaId\":\"02904CAE-71D2-45B3-9EC3-F6A9D18B6307\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.13\",\"versionEndExcluding\":\"6.18.23\",\"matchCriteriaId\":\"E9E09FDD-9EE3-4A56-92E2-2B30AFD0072F\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.19\",\"versionEndExcluding\":\"6.19.13\",\"matchCriteriaId\":\"1490EF9B-9080-481C-8D22-1306AAE664E4\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:5.12:-:*:*:*:*:*:*\",\"matchCriteriaId\":\"75EB504D-4A83-4C67-9C8D-FD9C6C8EB4CD\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*\",\"matchCriteriaId\":\"F253B622-8837-4245-BCE5-A7BF8FC76A16\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*\",\"matchCriteriaId\":\"4AE85AD8-4641-4E7C-A2F4-305E2CD9EE64\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*\",\"matchCriteriaId\":\"F666C8D8-6538-46D4-B318-87610DE64C34\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*\",\"matchCriteriaId\":\"02259FDA-961B-47BC-AE7F-93D7EC6E90C2\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*\",\"matchCriteriaId\":\"58A9FEFF-C040-420D-8F0A-BFDAAA1DF258\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*\",\"matchCriteriaId\":\"1D2315C0-D46F-4F85-9754-F9E5E11374A6\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:*\",\"matchCriteriaId\":\"512EE3A8-A590-4501-9A94-5D4B268D6138\"}]}]}],\"references\":[{\"url\":\"https://git.kernel.org/stable/c/15fa9ead4d5e6b6b9c794e84144146c917f2cb62\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/3fd6547f5b8ac99687be6d937a0321efda760597\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/9b55b253907e7431210483519c5ad711a37dafa1\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/b313e9037d98c13938740e5ebda7852929366dff\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/eb9c6aeb512f877cf397deb1e4526f646c70e4a7\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/f6e1f25fa5e733570f6d6fe37a4dfed2a0deba47\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/fb1f54b7d16f393b8b65d328410f78b4beea8fcc\",\"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.