{"id":"CVE-2026-89554","summary":"mptcp: fix uninitialized local_id in syncookie MP_JOIN reconstruction","details":"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-\u003elocal_id from the cookie entry, as done for the other\nfields.","modified":"2026-09-25T18:26:54.499691231Z","published":"2026-09-11T19:44:27.586Z","related":["openSUSE-SU-2026:11880-1"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89554.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/4534e0eead692bb069ad1e6a5a245fc2e2078300"},{"type":"WEB","url":"https://git.kernel.org/stable/c/51887ccd88791ddaa8755a7c614fda031ecf7982"},{"type":"WEB","url":"https://git.kernel.org/stable/c/63cacb05e51a1c6e1349d2e593d00fd6ef43def4"},{"type":"WEB","url":"https://git.kernel.org/stable/c/64f2c5dd49b956a542c8c02b8dad5d262a462bba"},{"type":"WEB","url":"https://git.kernel.org/stable/c/954b5ea836eb118d188975ced803448537ab8479"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9df36a4846375a9b75bf42d77bfed216b0f366f9"},{"type":"WEB","url":"https://git.kernel.org/stable/c/b878dfdd12d7a5b8722a78d35e313506140ca3d9"},{"type":"WEB","url":"https://git.kernel.org/stable/c/bf19d166337c6488b39cb03eeeffb30a941d6326"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89554.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89554"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"9466a1ccebbe54ac57fb8a89c2b4b854826546a8"},{"fixed":"4534e0eead692bb069ad1e6a5a245fc2e2078300"},{"fixed":"63cacb05e51a1c6e1349d2e593d00fd6ef43def4"},{"fixed":"954b5ea836eb118d188975ced803448537ab8479"},{"fixed":"9df36a4846375a9b75bf42d77bfed216b0f366f9"},{"fixed":"64f2c5dd49b956a542c8c02b8dad5d262a462bba"},{"fixed":"51887ccd88791ddaa8755a7c614fda031ecf7982"},{"fixed":"bf19d166337c6488b39cb03eeeffb30a941d6326"},{"fixed":"b878dfdd12d7a5b8722a78d35e313506140ca3d9"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-89554.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.9.0"},{"fixed":"5.10.270"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.221"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.188"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.157"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.109"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.50"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.4"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-89554.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H"}]}