CVE-2026-89554mptcp: fix uninitialized local_id in syncookie MP_JOIN reconstruction
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 8.2 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
- Weakness (CWE)
- Not given
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Linux
- NVD analysis
- Received
- Record last updated
- Oct 16, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Linux Linux linux:linux (from the name) | 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 builds before 4534e0eead692bb069ad1e6a5a245fc2e2078300; 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 builds before 63cacb05e51a1c6e1349d2e593d00fd6ef43def4; 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 builds before 954b5ea836eb118d188975ced803448537ab8479; 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 builds before 9df36a4846375a9b75bf42d77bfed216b0f366f9; 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 builds before 64f2c5dd49b956a542c8c02b8dad5d262a462bba; from 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 before 51887ccd88791ddaa8755a7c614fda031ecf7982; from 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 before bf19d166337c6488b39cb03eeeffb30a941d6326; from 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 before b878dfdd12d7a5b8722a78d35e313506140ca3d9 | CNA record |
References
- https://git.kernel.org/stable/c/4534e0eead692bb069ad1e6a5a245fc2e2078300
- https://git.kernel.org/stable/c/63cacb05e51a1c6e1349d2e593d00fd6ef43def4
- https://git.kernel.org/stable/c/954b5ea836eb118d188975ced803448537ab8479
- https://git.kernel.org/stable/c/9df36a4846375a9b75bf42d77bfed216b0f366f9
- https://git.kernel.org/stable/c/64f2c5dd49b956a542c8c02b8dad5d262a462bba
- https://git.kernel.org/stable/c/51887ccd88791ddaa8755a7c614fda031ecf7982
- https://git.kernel.org/stable/c/bf19d166337c6488b39cb03eeeffb30a941d6326
- https://git.kernel.org/stable/c/b878dfdd12d7a5b8722a78d35e313506140ca3d9
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.