CVE-2026-89554

Last refreshed2026-10-17

Status: UPDATED | Advisory ID: CVE-2026-89554

Key Details

CVE	CVE-2026-89554
CVSS Score / Version	8.2 (High) / CVSS v3.1
Updated	2026-10-16
CVSS Vector	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H`
CVSS Prose	attack vector is network; attack complexity is low; privileges required is none; user interaction is none; scope is unchanged; confidentiality impact is none; integrity impact is low; availability impact is high.
Affected products	Linux Kernel

Vendor	Product	Affected Versions	Patch Status
Linux	Linux Kernel

Vendor

Product

Affected Versions

Patch Status

Linux

Linux Kernel

Subsystems	OT Supporting Infrastructure
Sectors	All Sectors

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. (NVD)

Monitor Linux's web page for any future patch releases.

Source	Reference
NVD	https://nvd.nist.gov/vuln/detail/CVE-2026-89554
CVE	https://www.cve.org/CVERecord?id=CVE-2026-89554

Source

Reference

NVD

CVE