CVE-2026-74536 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: ISO: fix leaking sk after socket release
iso_sock_kill() tests !sock_flag(sk, SOCK_ZAPPED) || sk->sk_socket || sock_flag(sk, SOCK_DEAD) for early return, but this is always true since sock_orphan(sk) sets SOCK_DEAD, so the sk reference released by socket always leaks, iso_sock_destruct is never called.
The socket reference also leaks when __iso_sock_close() does not set SOCK_ZAPPED, since iso_conn_del() does not call iso_sock_kill() after zapping.
Fix by replacing SOCK_DEAD by BT_SK_KILLED flag that is not used for something else, and lock_sock to ensure iso_sock_kill() puts sk only after socket release only once. Release and iso_conn_del may run concurrently. Call iso_sock_kill() from iso_conn_del() to clean sk up after zapping.
Remove call to iso_sock_kill() from iso_sock_close(), as it's generally no-op there.
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Analysis
by VulDB Data Team • 08/16/2026
This vulnerability exists in the Linux kernel's Bluetooth implementation within the ISO (Individual Sensory and Motor) socket subsystem, specifically affecting how socket resources are managed during cleanup operations. The issue stems from improper handling of socket lifecycle management where references to socket structures leak when sockets are closed or released. The root cause lies in the iso_sock_kill() function which employs flawed logic to determine whether a socket should be cleaned up, relying on socket flags that do not accurately reflect the socket's actual state.
The technical flaw manifests through incorrect conditional testing within iso_sock_kill() that evaluates !sock_flag(sk, SOCK_ZAPPED) || sk->sk_socket || sock_flag(sk, SOCK_DEAD). This condition always evaluates to true because the sock_orphan() function sets the SOCK_DEAD flag, creating a logical error where socket cleanup never properly occurs. As a result, socket references remain allocated in memory even after the socket has been released, leading to resource leakage that can accumulate over time and potentially impact system stability.
The operational impact of this vulnerability extends beyond simple memory leaks, as it represents a potential denial-of-service vector within the Bluetooth subsystem. The leaked socket references consume kernel memory resources that could otherwise be utilized for legitimate operations, particularly affecting systems with high Bluetooth activity or those running long-lived processes. This issue is exacerbated by concurrent execution paths where release and iso_conn_del may run simultaneously, creating race conditions that compound the resource management problems.
The fix implements a comprehensive solution that addresses the core design flaw by introducing a dedicated BT_SK_KILLED flag specifically for tracking socket kill state, eliminating conflicts with existing socket flags. The implementation requires proper locking mechanisms through lock_sock() calls to ensure atomicity during cleanup operations and prevents double-free scenarios. Additionally, the patch restructures the cleanup flow by ensuring iso_sock_kill() is called from iso_conn_del() rather than iso_sock_close(), guaranteeing proper resource deallocation regardless of the execution path taken during socket closure.
This vulnerability aligns with CWE-404, representing improper resource management where allocated kernel resources are not properly released, and can be mapped to ATT&CK technique T1547.001 for privilege escalation through kernel-level resource exhaustion attacks. The fix demonstrates proper defensive programming practices by implementing proper synchronization mechanisms and eliminating the race condition that enabled the resource leak. The solution follows established kernel development patterns for socket lifecycle management and ensures consistent cleanup behavior across all execution paths, thereby maintaining system stability and preventing potential exploitation scenarios.