{"api_version":"1","generated_at":"2026-09-12T11:23:58+00:00","cve":"CVE-2026-89554","urls":{"html":"https://cve.report/CVE-2026-89554","api":"https://cve.report/api/cve/CVE-2026-89554.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-89554","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-89554"},"summary":{"title":"mptcp: fix uninitialized local_id in syncookie MP_JOIN reconstruction","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nmptcp: fix uninitialized local_id in syncookie MP_JOIN reconstruction\n\nmptcp_token_join_cookie_init_state() restores remote_nonce, local_nonce,\nbackup, join_id, token and msk from the saved cookie entry when rebuilding\nthe request socket for a MP_JOIN 4th-ACK handled under SYN cookies, but it\ndoes not restore local_id, even though the SYN path saved it.\nsubflow_ulp_clone() then reads that uninitialized field and stores it as\nthe joined subflow's address-ID. Because the request-sock slab is\nSLAB_TYPESAFE_BY_RCU and not zeroed on allocation, the value is the stale\nbyte of a previously freed request socket, which an off-path peer can\ninfluence by sending concurrent MP_JOIN SYNs. This corrupts the path\nmanager's id-based subflow bookkeeping for the connection.\n\nRestore subflow_req->local_id from the cookie entry, as done for the other\nfields.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-09-11 20:19:39","updated_at":"2026-09-11 20:19:39"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/64f2c5dd49b956a542c8c02b8dad5d262a462bba","name":"https://git.kernel.org/stable/c/64f2c5dd49b956a542c8c02b8dad5d262a462bba","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/51887ccd88791ddaa8755a7c614fda031ecf7982","name":"https://git.kernel.org/stable/c/51887ccd88791ddaa8755a7c614fda031ecf7982","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/b878dfdd12d7a5b8722a78d35e313506140ca3d9","name":"https://git.kernel.org/stable/c/b878dfdd12d7a5b8722a78d35e313506140ca3d9","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/bf19d166337c6488b39cb03eeeffb30a941d6326","name":"https://git.kernel.org/stable/c/bf19d166337c6488b39cb03eeeffb30a941d6326","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89554","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89554","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 64f2c5dd49b956a542c8c02b8dad5d262a462bba git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 51887ccd88791ddaa8755a7c614fda031ecf7982 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 bf19d166337c6488b39cb03eeeffb30a941d6326 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 b878dfdd12d7a5b8722a78d35e313506140ca3d9 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 5.9","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.9 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.109 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.50 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.4 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3-rc1 * 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/syncookies.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"64f2c5dd49b956a542c8c02b8dad5d262a462bba","status":"affected","version":"9466a1ccebbe54ac57fb8a89c2b4b854826546a8","versionType":"git"},{"lessThan":"51887ccd88791ddaa8755a7c614fda031ecf7982","status":"affected","version":"9466a1ccebbe54ac57fb8a89c2b4b854826546a8","versionType":"git"},{"lessThan":"bf19d166337c6488b39cb03eeeffb30a941d6326","status":"affected","version":"9466a1ccebbe54ac57fb8a89c2b4b854826546a8","versionType":"git"},{"lessThan":"b878dfdd12d7a5b8722a78d35e313506140ca3d9","status":"affected","version":"9466a1ccebbe54ac57fb8a89c2b4b854826546a8","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["net/mptcp/syncookies.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"5.9"},{"lessThan":"5.9","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.109","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.50","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.4","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3-rc1","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.109","versionStartIncluding":"5.9","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.50","versionStartIncluding":"5.9","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.4","versionStartIncluding":"5.9","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3-rc1","versionStartIncluding":"5.9","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nmptcp: fix uninitialized local_id in syncookie MP_JOIN reconstruction\n\nmptcp_token_join_cookie_init_state() restores remote_nonce, local_nonce,\nbackup, join_id, token and msk from the saved cookie entry when rebuilding\nthe request socket for a MP_JOIN 4th-ACK handled under SYN cookies, but it\ndoes not restore local_id, even though the SYN path saved it.\nsubflow_ulp_clone() then reads that uninitialized field and stores it as\nthe joined subflow's address-ID. Because the request-sock slab is\nSLAB_TYPESAFE_BY_RCU and not zeroed on allocation, the value is the stale\nbyte of a previously freed request socket, which an off-path peer can\ninfluence by sending concurrent MP_JOIN SYNs. This corrupts the path\nmanager's id-based subflow bookkeeping for the connection.\n\nRestore subflow_req->local_id from the cookie entry, as done for the other\nfields."}],"providerMetadata":{"dateUpdated":"2026-09-11T19:44:27.586Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/64f2c5dd49b956a542c8c02b8dad5d262a462bba"},{"url":"https://git.kernel.org/stable/c/51887ccd88791ddaa8755a7c614fda031ecf7982"},{"url":"https://git.kernel.org/stable/c/bf19d166337c6488b39cb03eeeffb30a941d6326"},{"url":"https://git.kernel.org/stable/c/b878dfdd12d7a5b8722a78d35e313506140ca3d9"}],"title":"mptcp: fix uninitialized local_id in syncookie MP_JOIN reconstruction","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-89554","datePublished":"2026-09-11T19:44:27.586Z","dateReserved":"2026-09-11T19:38:34.724Z","dateUpdated":"2026-09-11T19:44:27.586Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-11 20:19:39","lastModifiedDate":"2026-09-11 20:19:39","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"89554","Ordinal":"1","Title":"mptcp: fix uninitialized local_id in syncookie MP_JOIN reconstru","CVE":"CVE-2026-89554","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"89554","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nmptcp: fix uninitialized local_id in syncookie MP_JOIN reconstruction\n\nmptcp_token_join_cookie_init_state() restores remote_nonce, local_nonce,\nbackup, join_id, token and msk from the saved cookie entry when rebuilding\nthe request socket for a MP_JOIN 4th-ACK handled under SYN cookies, but it\ndoes not restore local_id, even though the SYN path saved it.\nsubflow_ulp_clone() then reads that uninitialized field and stores it as\nthe joined subflow's address-ID. Because the request-sock slab is\nSLAB_TYPESAFE_BY_RCU and not zeroed on allocation, the value is the stale\nbyte of a previously freed request socket, which an off-path peer can\ninfluence by sending concurrent MP_JOIN SYNs. This corrupts the path\nmanager's id-based subflow bookkeeping for the connection.\n\nRestore subflow_req->local_id from the cookie entry, as done for the other\nfields.","Type":"Description","Title":"mptcp: fix uninitialized local_id in syncookie MP_JOIN reconstru"}]}}}