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CVE-2025-21795 is a denial-of-service vulnerability in the Linux kernel NFSD NFSv4 callback shutdown path. When an nfs4_client is in courtesy state, NFSD can unnecessarily issue an RPC callback from nfsd4_run_cb_work. The callback leaves the client callback-inflight counter nonzero, causing nfsd4_shutdown_callback to wait until the TCP stack reports that the connection has dropped. The fix suppresses the RPC callback for clients in courtesy state.
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Linux kernel NFSD flaw involving a hang in nfsd4_shutdown_callback.
Linux kernel NFSD shutdown denial-of-service flaw.
A Linux kernel NFSD flaw in which shutdown callback handling can hang for approximately 15 minutes when an NFSv4 client is in courtesy state and a callback remains marked in flight. The fix skips the RPC callback in this state.
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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.