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CVE-2025-40186 is a TCP Fast Open (TFO) request-socket lifetime-management flaw in the Linux kernel TCP connection-request path. When a listening socket is closed while a TFO socket is processed by tcp_conn_request(), inet_csk_reqsk_queue_add() can invoke inet_child_forget() without setting reqsk->sk. inet_child_forget() invokes tcp_disconnect(), which removes and releases the TFO request socket. A subsequent reqsk_fastopen_remove() invocation in tcp_conn_request() can release the same request socket again, causing a request-socket and listener reference-count underflow, use-after-free, and double-free condition. The upstream correction removes reqsk_fastopen_remove() from tcp_conn_request().
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32 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A vulnerability addressed by the referenced CentOS 7 security advisory.
A Linux kernel TCP connection-request handling flaw involving incorrect use of reqsk_fastopen_remove().
CVE-2025-40186 is listed in the advisory's CVE references, but the content provides no technical description or explicit security-fix entry for it.
A Linux kernel vulnerability referenced in the advisory, for which the supplied content provides no technical description.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.