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CVE-2025-40133 is a use-after-free vulnerability in the Linux kernel Multipath TCP (MPTCP) subsystem. The mptcp_active_enable() function can be called through subflow_finish_connect() and the associated receive-destination setup path without guaranteed RCU protection. Its access to the destination device through sk_dst_get(sk)->dev can therefore dereference an object whose lifetime is no longer protected. The upstream fix replaces this access pattern with __sk_dst_get() and dst_dev_rcu() to safely obtain the destination device.
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No public exploit code observed for this vulnerability.
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Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
7 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A Linux kernel vulnerability in MPTCP related to use of destination lookup helpers in mptcp_active_enable().
A use-after-free vulnerability in the Linux kernel's Multipath TCP (MPTCP) path, where mptcp_active_enable() could access sk_dst_get(sk)->dev without always being protected by RCU.
A Linux kernel MPTCP vulnerability in mptcp_active_enable() related to destination handling and RCU-safe access.
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.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.