CVE-2026-68170

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

mptcp: fix stale skb->sk reference on subflow close

The backlog list is updated by mptcp_data_ready() under

mptcp_data_lock(). The cleanup of backlog references to a closing

subflow, however, was performed in mptcp_close_ssk(), before

__mptcp_close_ssk() acquires the ssk lock, and while holding neither

the ssk lock nor mptcp_data_lock().

Because that traversal ran without mptcp_data_lock(), concurrent softirq

RX processing on another CPU (subflow_data_ready() -> mptcp_data_ready()

-> __mptcp_add_backlog(), under mptcp_data_lock()) could add a backlog

entry referencing the ssk while the cleanup loop was in progress. Such

an entry could be missed by the cleanup, or the concurrent list update

could corrupt the traversal, leaving skb->sk pointing at the ssk after

it is freed.

A later mptcp_backlog_purge() then dereferences the stale pointer,

triggering a warning in inet_sock_destruct() (ssk->sk_rmem_alloc != 0)

followe

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References