{"api_version":"1","generated_at":"2026-04-25T12:38:15+00:00","cve":"CVE-2026-31669","urls":{"html":"https://cve.report/CVE-2026-31669","api":"https://cve.report/api/cve/CVE-2026-31669.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-31669","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-31669"},"summary":{"title":"mptcp: fix slab-use-after-free in __inet_lookup_established","description":"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's 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(&tcpv6_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.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-04-24 15:16:46","updated_at":"2026-04-24 17:51:40"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/fb1f54b7d16f393b8b65d328410f78b4beea8fcc","name":"https://git.kernel.org/stable/c/fb1f54b7d16f393b8b65d328410f78b4beea8fcc","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/3fd6547f5b8ac99687be6d937a0321efda760597","name":"https://git.kernel.org/stable/c/3fd6547f5b8ac99687be6d937a0321efda760597","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/f6e1f25fa5e733570f6d6fe37a4dfed2a0deba47","name":"https://git.kernel.org/stable/c/f6e1f25fa5e733570f6d6fe37a4dfed2a0deba47","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/15fa9ead4d5e6b6b9c794e84144146c917f2cb62","name":"https://git.kernel.org/stable/c/15fa9ead4d5e6b6b9c794e84144146c917f2cb62","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/9b55b253907e7431210483519c5ad711a37dafa1","name":"https://git.kernel.org/stable/c/9b55b253907e7431210483519c5ad711a37dafa1","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/eb9c6aeb512f877cf397deb1e4526f646c70e4a7","name":"https://git.kernel.org/stable/c/eb9c6aeb512f877cf397deb1e4526f646c70e4a7","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/b313e9037d98c13938740e5ebda7852929366dff","name":"https://git.kernel.org/stable/c/b313e9037d98c13938740e5ebda7852929366dff","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-31669","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31669","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected b19bc2945b40b9fd38e835700907ffe8534ef0de f6e1f25fa5e733570f6d6fe37a4dfed2a0deba47 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected b19bc2945b40b9fd38e835700907ffe8534ef0de fb1f54b7d16f393b8b65d328410f78b4beea8fcc git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected b19bc2945b40b9fd38e835700907ffe8534ef0de 3fd6547f5b8ac99687be6d937a0321efda760597 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected b19bc2945b40b9fd38e835700907ffe8534ef0de eb9c6aeb512f877cf397deb1e4526f646c70e4a7 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected b19bc2945b40b9fd38e835700907ffe8534ef0de 15fa9ead4d5e6b6b9c794e84144146c917f2cb62 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected b19bc2945b40b9fd38e835700907ffe8534ef0de b313e9037d98c13938740e5ebda7852929366dff git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected b19bc2945b40b9fd38e835700907ffe8534ef0de 9b55b253907e7431210483519c5ad711a37dafa1 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 5.12","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.12 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.15.203 5.15.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.1.169 6.1.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6.135 6.6.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.82 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.23 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.19.13 6.19.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.0 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"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's 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(&tcpv6_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."}],"providerMetadata":{"dateUpdated":"2026-04-24T14:45:17.295Z","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":"2026-04-24T14:45:17.295Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-04-24 15:16:46","lastModifiedDate":"2026-04-24 17:51:40","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"31669","Ordinal":"1","Title":"mptcp: fix slab-use-after-free in __inet_lookup_established","CVE":"CVE-2026-31669","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"31669","Ordinal":"1","NoteData":"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's 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(&tcpv6_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.","Type":"Description","Title":"mptcp: fix slab-use-after-free in __inet_lookup_established"}]}}}