CVE-2026-89554High· 8.2▾ TwilightIn the Linux kernel, the following vulnerability has been resolved: mptcp: fix uninitialized local_id in syncookie MP_JOIN reconstruction mptcp_token_join_cookie_init_state() restores remote_nonce, local_nonce, backup, join_id, token a…
▾ Twilight zone — High severity, or a signal on a lesser flaw
impact 45.1 · likelihood 0.1 · exploitation 0
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Stakeholder-Specific Vulnerability Categorization from CISA's ADP record at CVE.org: whether exploitation is observed, whether an attack can be automated, and how much of the system is at stake. The CVSS score shown above comes from the assigning CNA record, not NVD.
Exploit-prediction probability, daily snapshots since Sep 12.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via CVEORG
0.2%
— → 6.5
none → medium
— → 8.2
none → high
8.2 → 6.5
high → medium
6.5 → 8.2
medium → high
0.2% → 0.6%
8.2 → 5.5
high → medium
5.5 → 8.2
medium → high
Last analysed / modified upstream
In the Linux kernel, the following vulnerability has been resolved:
mptcp: fix uninitialized local_id in syncookie MP_JOIN reconstruction
mptcp_token_join_cookie_init_state() restores remote_nonce, local_nonce, backup, join_id, token and msk from the saved cookie entry when rebuilding the request socket for a MP_JOIN 4th-ACK handled under SYN cookies, but it does not restore local_id, even though the SYN path saved it. subflow_ulp_clone() then reads that uninitialized field and stores it as the joined subflow's address-ID. Because the request-sock slab is SLAB_TYPESAFE_BY_RCU and not zeroed on allocation, the value is the stale byte of a previously freed request socket, which an off-path peer can influence by sending concurrent MP_JOIN SYNs. This corrupts the path manager's id-based subflow bookkeeping for the connection.
Restore subflow_req->local_id from the cookie entry, as done for the other fields.
Linux >= 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 < 4534e0eead692bb069ad1e6a5a245fc2e2078300Linux >= 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 < 63cacb05e51a1c6e1349d2e593d00fd6ef43def4Linux >= 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 < 954b5ea836eb118d188975ced803448537ab8479Linux >= 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 < 9df36a4846375a9b75bf42d77bfed216b0f366f9Linux >= 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 < 64f2c5dd49b956a542c8c02b8dad5d262a462bbaLinux >= 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 < 51887ccd88791ddaa8755a7c614fda031ecf7982Linux >= 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 < bf19d166337c6488b39cb03eeeffb30a941d6326Linux >= 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 < b878dfdd12d7a5b8722a78d35e313506140ca3d9Linux 5.9Refer to the linked advisories for vendor-supplied fixes and affected version ranges.
Field changes observed since this record was first indexed.
Connected by shared product, vendor, weakness, or advisory.
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