CVE-2026-63973 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
net: mana: Add NULL guards in teardown path to prevent panic on attach failure
When queue allocation fails partway through, the error cleanup frees and NULLs apc->tx_qp and apc->rxqs. Multiple teardown paths such as mana_remove(), mana_change_mtu() recovery, and internal error handling in mana_alloc_queues() can subsequently call into functions that dereference these pointers without NULL checks:
- mana_chn_setxdp() dereferences apc->rxqs[0], causing a NULL pointer
dereference panic (CR2: 0000000000000000 at mana_chn_setxdp+0x26). - mana_destroy_vport() iterates apc->rxqs without a NULL check. - mana_fence_rqs() iterates apc->rxqs without a NULL check. - mana_dealloc_queues() iterates apc->tx_qp without a NULL check.
Add NULL guards for apc->rxqs in mana_fence_rqs(), mana_destroy_vport(), and before the mana_chn_setxdp() call. Add a NULL guard for apc->tx_qp in mana_dealloc_queues() to skip TX queue draining when TX queues were never allocated or already freed.
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Analysis
by VulDB Data Team • 07/19/2026
This vulnerability resides in the Linux kernel's network driver implementation for the Microsoft Azure Network Adapter MANA (Microsoft Azure Network Adapter) which is part of the net subsystem. The issue manifests as a potential system panic occurring during driver teardown operations when queue allocation fails midway through the initialization process. The vulnerability stems from inadequate null pointer validation within multiple cleanup paths that handle error conditions and driver removal scenarios.
The technical flaw involves improper resource management during error recovery in the MANA network adapter driver where memory allocated for transmission and reception queues gets freed and NULLed during early failure conditions, but subsequent cleanup functions fail to verify these pointers before dereferencing them. Specifically when queue allocation fails partway through the initialization process, the system correctly frees and sets apc->tx_qp and apc->rxqs to NULL as part of error cleanup procedures. However, various teardown functions including mana_remove(), mana_change_mtu() recovery routines, and internal error handling within mana_alloc_queues() do not perform proper NULL checks before accessing these previously freed pointers.
The operational impact of this vulnerability can result in system crashes and kernel panics when the driver encounters allocation failures during queue setup, particularly affecting systems running on Azure infrastructure that utilize the MANA network adapter. The panic occurs at specific memory addresses with CR2 values indicating null pointer dereference conditions, as demonstrated by the mana_chn_setxdp() function attempting to access apc->rxqs[0] when this pointer has already been NULLed during cleanup. This represents a classic security risk where an attacker could potentially trigger denial of service conditions through carefully crafted network operations that cause allocation failures.
The vulnerability aligns with CWE-476 which identifies NULL Pointer Dereference as a critical weakness in software design, and maps to ATT&CK technique T1499.004 for network denial of service attacks. Multiple functions within the driver codebase demonstrate this flaw including mana_fence_rqs() which iterates through apc->rxqs without null checking, mana_destroy_vport() performing similar operations, and mana_dealloc_queues() accessing apc->tx_qp without proper validation. The fix implements comprehensive null guards across all affected teardown paths to prevent access to freed memory locations while maintaining proper resource management during both successful and failed initialization scenarios.
This vulnerability represents a fundamental flaw in the driver's error handling mechanism that violates standard software development practices for robust resource management. The solution requires adding explicit NULL pointer checks before dereferencing shared resource pointers within cleanup routines, ensuring that functions properly handle cases where resources were never allocated or have already been freed during error recovery sequences. The mitigation approach directly addresses the root cause by preventing access to invalid memory locations while preserving the integrity of driver state management during both normal operation and exceptional failure conditions.