Linux Kernel Vulnerability in TCP Socket Handling by Google

CVE-2025-40186

What is CVE-2025-40186?

A vulnerability exists in the Linux kernel's TCP socket handling which can lead to a refcount underflow and potential memory corruption. This issue arises when a listener socket is closed while a TCP Fast Open (TFO) socket is being processed. The flaw occurs because certain functions do not correctly handle reference counting, which may result in a use-after-free condition. This could allow for unexpected behavior such as crashes or exploitation opportunities. It is critical for systems running affected kernel versions to apply the latest patches to mitigate this risk.

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