CVE-2022-48933 in Linux
Summary
by MITRE • 08/22/2024
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nf_tables: fix memory leak during stateful obj update
stateful objects can be updated from the control plane. The transaction logic allocates a temporary object for this purpose.
The ->init function was called for this object, so plain kfree() leaks resources. We must call ->destroy function of the object.
nft_obj_destroy does this, but it also decrements the module refcount, but the update path doesn't increment it.
To avoid special-casing the update object release, do module_get for the update case too and release it via nft_obj_destroy().
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Analysis
by VulDB Data Team • 11/25/2024
The vulnerability identified as CVE-2022-48933 resides within the Linux kernel's netfilter subsystem, specifically in the nf_tables framework that manages stateful network object operations. This issue represents a memory management flaw that occurs during the update process of stateful objects, which are critical components for maintaining connection tracking and stateful packet filtering in network security policies. The vulnerability manifests when the kernel's transaction logic attempts to update existing stateful objects through the control plane interface, creating a scenario where resource cleanup operations fail to properly release allocated memory.
The technical root cause of this vulnerability stems from improper object lifecycle management within the nf_tables subsystem. When stateful objects undergo updates, the kernel's transaction logic allocates temporary objects to facilitate the modification process. During this allocation, the system correctly invokes the object's initialization function through the ->init method, but fails to properly handle the cleanup phase. The standard kfree() operation used for simple memory deallocation is insufficient for objects that require specialized destruction functions to release their allocated resources. This oversight creates a memory leak where resources associated with the temporary object remain allocated even after the update operation completes, leading to gradual memory consumption over time.
The operational impact of this vulnerability extends beyond simple memory exhaustion, potentially affecting system stability and performance in environments heavily reliant on netfilter stateful operations. Attackers could exploit this weakness by repeatedly triggering stateful object updates, causing progressive memory consumption that may eventually lead to system instability or denial of service conditions. The vulnerability is particularly concerning in high-throughput network environments where frequent connection tracking updates occur, as the memory leak compounds over time and could impact the overall system responsiveness and resource availability. Network security appliances, firewalls, and routers running Linux kernels with affected versions would be especially vulnerable to this type of resource exhaustion attack.
Mitigation strategies for CVE-2022-48933 focus on implementing proper module reference counting and object destruction protocols during stateful object updates. The fix addresses the issue by ensuring that module reference counts are properly incremented for update operations, allowing the nft_obj_destroy function to correctly handle both the object's destruction and module reference decrement in a consistent manner. This approach eliminates the need for special-case handling of update objects and ensures that all object cleanup paths follow the same consistent pattern. System administrators should prioritize applying kernel updates that include this fix, particularly in production environments where network security and system stability are paramount. The vulnerability aligns with CWE-401, which addresses improper release of memory, and falls under ATT&CK technique T1499.001 for resource exhaustion, making it a significant concern for security teams managing network infrastructure components.