CVE-2026-89554

CVE CVE-2026-89554EUVD EUVD-2026-76465Published 2026-09-11T19:44:27.000ZLast changed 2026-09-14T12:00:56.000ZCVSS 8.2

What the advisory describes

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.

Source: EUVD (ENISA), in the words of the advisory.

Products the advisory names

These come from the advisory itself, not from any check we performed.

Linux — Linux patch: 7.3-rc1; 5.9; 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 <4534e0eead692bb069ad1e6a5a245fc2e2078300; 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 <9df36a4846375a9b75bf42d77bfed216b0f366f9; patch: 6.12.109; 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 <64f2c5dd49b956a542c8c02b8dad5d262a462bba; 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 <bf19d166337c6488b39cb03eeeffb30a941d6326; patch: 6.1.188; patch: 6.6.157; patch: 6.18.50; 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 <b878dfdd12d7a5b8722a78d35e313506140ca3d9; 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 <954b5ea836eb118d188975ced803448537ab8479; 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 <51887ccd88791ddaa8755a7c614fda031ecf7982; 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 <63cacb05e51a1c6e1349d2e593d00fd6ef43def4; patch: 5.15.221; patch: 7.2.4; patch: 5.10.270; patch: 0

The versions shown are the advisory's own. Patchlage compares no version numbers and derives no judgement from them — which version is installed is something a person has to look up.

Carried in the product catalogue

An estate covering these products can be recorded in Patchlage. An advisory about them appears in the next morning's situation report.

Linux — Linux

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