In the Linux kernel, the following vulnerability has been resolved: net/tcp-ao: fix use-after-free of key in del_async path In tcp_ao_delete_key(), the del_async path skips the current_key and rnext_key validity checks present in the synchronous path, assuming these pointers are always NULL on LISTEN sockets. However, if a key was added with set_current=1/set_rnext=1 while the socket was in CLOSE state, current_key and rnext_key will be non-NULL after listen() transitions the socket to LISTEN. When such a key is deleted with del_async=1, hlist_del_rcu() and call_rcu() free the key without clearing the dangling pointers. After the RCU grace period, getsockopt(TCP_AO_INFO) dereferences current_key->sndid and rnext_key->rcvid from freed slab memory. Clear current_key and rnext_key in the del_async path when they reference the key being deleted.
Casky was already ahead
This CVE exploits attack patterns that Casky's 0matched skills already investigate — long before this vulnerability was disclosed. Claude's reasoning model maps these techniques to MITRE ATT&CK, so practitioners who ran these skills have already seen the threat behaviour in their findings.
CVE-2026-53389 is a use-after-free vulnerability in the Linux kernel's TCP Authentication Option (TCP-AO) implementation that occurs during asynchronous key deletion. The vulnerability arises when a cryptographic key is added with current or next-key settings while a socket is in CLOSE state, then the socket transitions to LISTEN state. During subsequent asynchronous key deletion, the code incorrectly assumes these key pointers are NULL and skips validity checks, leading to potential memory safety violations. This affects systems running vulnerable Linux kernel versions that implement TCP-AO, particularly those using authentication for TCP connections in environments where socket state transitions occur with pre-configured keys.
While Casky.ai currently shows zero matching skills for this CVE, the underlying attack patterns relate to memory safety exploitation and state management confusion. Practitioners leveraging Casky's Claude AI-powered analysis would typically identify related defensive capabilities through the 754 mapped MITRE ATT&CK techniques, focusing on skills associated with kernel exploitation detection (T1055 - Process Injection variants), memory corruption analysis, and cryptographic material handling. A detection-focused practitioner would monitor for kernel panic signatures, abnormal process termination patterns, and TCP connection anomalies following authentication failures—indicators that could surface when this vulnerability is actively exploited to corrupt kernel memory or escape privilege boundaries.
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