CVE-2026-89536
CriticalCVSS 9.8Exploitation Probability (EPSS)
Low risk10th percentile - higher than 10% of all known CVEs
Summary
In the Linux kernel, xs_tls_handshake_sync() in the SUNRPC subsystem has a use-after-free race during TLS handshake cancellation. When handshake_req_cancel() returns false (because handshake_complete() already marked the request complete), the waiter may drop the lower transport reference before the xs_tls_handshake_done() callback finishes. This can free the transport while it is still in use.
Risk Assessment
Can cause kernel memory corruption, system crashes, or potential exploitation by an attacker able to trigger a timeout or signal during TLS handshake. Affects SUNRPC clients using TLS.
Recommendation
Update the Linux kernel to a version containing the fix that, when cancellation loses to completion, waits for xs_tls_handshake_done() to signal handshake_done and lets the callback release its reference.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: SUNRPC: wait for in-flight client TLS handshake callback xs_tls_handshake_sync() gives xs_tls_handshake_done() a reference to the lower transport before submitting the handshake request. On timeout or signal, the synchronous waiter drops that reference after calling tls_handshake_cancel(). handshake_req_cancel() returns false when handshake_complete() has already marked the request complete. In that case the completion callback can still be running, so dropping the callback-owned reference in the waiter can free the lower transport before xs_tls_handshake_done() stores xprt_err or drops its own reference. If cancellation loses to completion, wait until xs_tls_handshake_done() signals handshake_done and let the callback release its reference. This mirrors the server-side handshake lifetime handling and keeps the timeout or signal return value unchanged.