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CVE-2025-21791 is a potential use-after-free vulnerability in the Linux kernel Virtual Routing and Forwarding (VRF) networking implementation. The l3mdev_l3_out() output-path function can be reached from raw_sendmsg() via the IPv4 local-output path without an RCU read-side critical section. Concurrent modification or teardown of an RCU-protected object could therefore permit l3mdev_l3_out() to access freed memory. The upstream fix wraps the relevant operations in rcu_read_lock() and rcu_read_unlock().
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A Linux kernel VRF vulnerability involving missing RCU protection in l3mdev_l3_out().
Linux kernel VRF RCU synchronization flaw.
A Linux kernel VRF networking use-after-free vulnerability caused by l3mdev_l3_out() being callable without RCU protection. The fix adds an rcu_read_lock()/rcu_read_unlock() pair.
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Every observed campaign linking this CVE to a named adversary.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.