CVE-2025-71084 in Linux
Summary
by MITRE • 01/13/2026
In the Linux kernel, the following vulnerability has been resolved:
RDMA/cm: Fix leaking the multicast GID table reference
If the CM ID is destroyed while the CM event for multicast creating is still queued the cancel_work_sync() will prevent the work from running which also prevents destroying the ah_attr. This leaks a refcount and triggers a WARN:
GID entry ref leak for dev syz1 index 2 ref=573 WARNING: CPU: 1 PID: 655 at drivers/infiniband/core/cache.c:809 release_gid_table drivers/infiniband/core/cache.c:806 [inline]
WARNING: CPU: 1 PID: 655 at drivers/infiniband/core/cache.c:809 gid_table_release_one+0x284/0x3cc drivers/infiniband/core/cache.c:886
Destroy the ah_attr after canceling the work, it is safe to call this twice.
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Analysis
by VulDB Data Team • 03/31/2026
The vulnerability CVE-2025-71084 affects the Linux kernel's RDMA communication manager component, specifically within the InfiniBand core subsystem. This issue represents a reference count leak in the multicast GID (Global Identifier) table management functionality that can lead to resource exhaustion and system instability. The vulnerability occurs when a communication manager identifier is destroyed while a multicast creation event is still queued in the system's work queue. This particular flaw demonstrates a classic race condition scenario where asynchronous operations are not properly synchronized with resource cleanup operations.
The technical root cause stems from improper ordering of operations within the RDMA communication manager's cleanup sequence. When cancel_work_sync() is invoked to prevent execution of pending multicast creation work items, it effectively blocks the work from running but fails to properly destroy the associated address handle attributes. This creates a situation where the ah_attr structure remains allocated and referenced even after the CM ID destruction process has begun. The reference count tracking mechanism in the InfiniBand core cache subsystem detects this inconsistency and triggers a kernel warning message indicating a GID entry reference leak. The warning specifically references drivers/infiniband/core/cache.c at line 809, where the release_gid_table function fails to properly decrement reference counts due to the incomplete cleanup sequence.
This vulnerability operates at the kernel level and can be exploited by malicious actors who have access to the system to potentially cause resource exhaustion attacks. The operational impact includes system instability, performance degradation, and potential denial of service conditions. The warning message indicates that a GID entry with index 2 on device syz1 has a reference count of 573, suggesting significant resource accumulation that could eventually exhaust available memory or system resources. The issue affects systems utilizing InfiniBand RDMA capabilities, particularly those implementing multicast communication patterns where multiple nodes need to communicate simultaneously. The vulnerability aligns with CWE-404, which describes improper resource release or unbalanced resource management, and could potentially be leveraged as part of broader attack chains targeting kernel memory management subsystems.
The fix implemented addresses this by reordering the cleanup operations to ensure that ah_attr destruction occurs after cancel_work_sync() is called but before the CM ID destruction completes. This approach ensures that all pending work items are properly cancelled and their associated resources are released before the parent structure is fully destroyed. The solution is considered safe because the ah_attr destruction function can be called twice without adverse effects, providing a robust defense against race conditions. System administrators should apply the kernel patch immediately to prevent exploitation, particularly in environments where InfiniBand RDMA is actively used for high-performance computing or data center networking. The mitigation strategy aligns with ATT&CK technique T1068, which involves exploiting local system vulnerabilities, and represents a critical kernel-level security fix that should be prioritized in all production environments using affected Linux kernel versions.