CVE-2025-21975 in Linux
Summary
by MITRE • 04/01/2025
In the Linux kernel, the following vulnerability has been resolved:
net/mlx5: handle errors in mlx5_chains_create_table()
In mlx5_chains_create_table(), the return value of mlx5_get_fdb_sub_ns() and mlx5_get_flow_namespace() must be checked to prevent NULL pointer dereferences. If either function fails, the function should log error message with mlx5_core_warn() and return error pointer.
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Analysis
by VulDB Data Team • 02/01/2026
The vulnerability identified as CVE-2025-21975 resides within the Linux kernel's mlx5 network driver subsystem, specifically affecting the mlx5_chains_create_table() function. This issue represents a classic null pointer dereference vulnerability that can lead to system instability and potential privilege escalation. The mlx5 driver supports Mellanox ConnectX series network adapters and operates at a critical layer of the kernel's networking stack, making this flaw particularly concerning for enterprise and data center environments where these adapters are commonly deployed.
The technical flaw manifests in the improper handling of error conditions within the mlx5_chains_create_table() function where the return values from two critical subsystem calls are not being validated. Specifically, mlx5_get_fdb_sub_ns() and mlx5_get_flow_namespace() functions are invoked without checking their return codes for failure conditions. When these functions encounter errors during namespace retrieval or FDB (Forwarding Database) sub-namespace initialization, they may return NULL pointers instead of valid namespace structures. The absence of proper error checking in the calling function leads to direct dereference of these potentially NULL values, resulting in kernel crashes or undefined behavior.
This vulnerability operates at the kernel level and can be exploited by malicious actors to cause denial of service conditions or potentially escalate privileges within the system. The impact extends beyond simple system crashes as the affected driver is integral to network functionality, particularly in high-performance computing environments and data center infrastructures where Mellanox adapters are prevalent. The flaw affects systems running Linux kernels with the mlx5 driver and could be exploited by local users or potentially remote attackers depending on system configuration and network access patterns. According to CWE classification, this represents a CWE-476: NULL Pointer Dereference vulnerability, which is categorized under the broader category of memory safety issues.
The operational impact of this vulnerability is significant for organizations relying on Mellanox network adapters in production environments. System administrators may experience unexpected service disruptions, kernel panics, or complete system crashes when the affected code path is triggered through normal network operations or malicious input. The vulnerability is particularly dangerous in cloud computing environments and containerized deployments where network performance and reliability are critical. Network traffic handling through the mlx5 driver could be compromised, leading to data loss or service interruption. From an ATT&CK framework perspective, this vulnerability could be leveraged for privilege escalation or persistence mechanisms, though the primary threat vector is denial of service.
Mitigation strategies for CVE-2025-21975 should focus on immediate kernel updates from the vendor, as the fix involves proper error code validation and logging within the mlx5 driver code. System administrators should prioritize patching affected systems, particularly in environments where Mellanox network adapters are actively used. The recommended approach includes monitoring system logs for mlx5_core_warn() messages that would indicate the occurrence of the error conditions that previously led to crashes. Additionally, implementing proper intrusion detection systems that monitor for unusual network behavior or kernel panic events can help identify exploitation attempts. Organizations should also consider implementing network segmentation and access controls to limit potential attack surfaces. The fix implemented in the patched kernel version ensures that error conditions are properly handled with appropriate logging and return value management, preventing the NULL pointer dereference scenario that previously occurred.