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.
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Amazon Linux Ami 2 | — | Upgrade bpftoolUpgrade kernel-debuginfo-common-aarch64Upgrade kernel-livepatch-5.15.221-157.262Upgrade kernel-debuginfoUpgrade kernel-tools-debuginfoUpgrade kernel-livepatch-5.10.270-271.1109Upgrade kernel-tools-develUpgrade perfUpgrade kernel-develUpgrade kernelUpgrade python-perfUpgrade kernel-toolsUpgrade bpftool-debuginfoUpgrade kernel-debuginfo-common-x86_64Upgrade kernel-headersUpgrade python-perf-debuginfoUpgrade perf-debuginfo | Oct 19, 2026 | Oct 19, 2026 |
| Amazon_linux_2023 | — | Upgrade kernel-tools-develUpgrade kernel-toolsUpgrade perf-debuginfoUpgrade kernel-debuginfo-common-aarch64Upgrade perfUpgrade kernel-headersUpgrade kernel-modules-extra-commonUpgrade python3-perfUpgrade bpftool-debuginfoUpgrade kernel-livepatch-6.1.188-233.385Upgrade kernel-modules-extraUpgrade bpftoolUpgrade python3-perf-debuginfoUpgrade kernelUpgrade kernel-debuginfo-common-x86_64Upgrade kernel-tools-debuginfoUpgrade kernel-debuginfoUpgrade kernel-devel | Oct 13, 2026 | Sep 11, 2026 |
| Debian | — | Upgrade linuxUpgrade linux-6.12 | Sep 30, 2026 | Sep 11, 2026 |
| Redhat_linux | — | No solution exists | Sep 16, 2026 | Sep 11, 2026 |
| Vmware Photon_os | — | Use 'tdnf update' to upgrade all packages to the latest version. | Sep 21, 2026 | Sep 11, 2026 |
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