CVE-2026-45889

Summary

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

mptcp: do not account for OoO in mptcp_rcvbuf_grow()

MPTCP-level OoOs are physiological when multiple subflows are active concurrently and will not cause retransmissions nor are caused by drops.

Accounting for them in mptcp_rcvbuf_grow() causes the rcvbuf slowly drifting towards tcp_rmem[2].

Remove such accounting. Note that subflows will still account for TCP-level OoO when the MPTCP-level rcvbuf is propagated.

This also closes a subtle and very unlikely race condition with rcvspace init; active sockets with user-space holding the msk-level socket lock, could complete such initialization in the receive callback, after that the first OoO data reaches the rcvbuf and potentially triggering a divide by zero Oops.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/fb7bf00b04a6b48859f52035d4e745848c2b4c79
• https://git.kernel.org/stable/c/400ee4854adef1e4983812a3decf6717ea020136
• https://git.kernel.org/stable/c/6b329393502e5857662b851a13f947209c588587

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