CVE-2026-74565 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nf_tables: make nft_object rhltable per table
The nft_object rhltable is global, this allows for accessing objects that are being dismangled from lookup path by other existing netns. Given the nft_obj_destroy() releases the object inmediately, this might lead to use-after-free of these objects that are being released. Make the existing rhltable per table to address this issue to deal with with the nft_rcv_nl_event() path too.
Update nft_obj_lookup() to take the table as non-const, otherwise, compiler complains when passing the objname_ht to rhltable_lookup().
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Analysis
by VulDB Data Team • 08/15/2026
The vulnerability in question relates to a use-after-free condition within the Linux kernel's netfilter subsystem, specifically in the nftables implementation. This flaw exists in the handling of nft_object structures and their associated rhltable (read-mostly hash table) data structure that maintains object references. The core issue stems from the global nature of the nft_object rhltable which creates a race condition scenario where objects being destroyed in one network namespace can still be accessed by lookup operations occurring in different network namespaces.
The technical flaw manifests when the nft_obj_destroy() function immediately releases memory for objects that are currently being accessed through the lookup path in other network namespaces. This immediate deallocation creates a window where previously freed memory locations might still be referenced, leading to potential memory corruption and system instability. The vulnerability is particularly concerning because it operates at the kernel level where such memory management errors can result in privilege escalation or complete system compromise.
This issue impacts the operational integrity of systems running Linux kernels with netfilter nftables functionality, especially those handling multiple network namespaces concurrently. The use-after-free condition can be exploited to cause system crashes, data corruption, or potentially allow malicious actors to execute arbitrary code with kernel privileges. The vulnerability affects systems where nftables is actively used for packet filtering and network address translation, particularly in environments managing complex network configurations across multiple namespaces.
The fix implements a per-table rhltable design pattern rather than maintaining a global structure, which isolates object references within specific table boundaries and prevents cross-namespace access during object destruction. This architectural change ensures that when objects are being destroyed, they cannot be simultaneously accessed by lookup operations in different network namespaces. The update also modifies nft_obj_lookup() to accept the table parameter as non-constant, resolving compiler warnings while maintaining proper function signatures for rhltable_lookup() operations.
This vulnerability aligns with CWE-416, which describes use-after-free conditions in memory management, and demonstrates characteristics consistent with ATT&CK technique T1068, which involves local privilege escalation through kernel vulnerabilities. The fix addresses fundamental race condition issues in kernel object lifecycle management and represents a critical security enhancement for systems relying on nftables functionality.
The mitigation strategy involves applying the kernel patch that implements per-table rhltable structures and ensures proper synchronization between object destruction and lookup operations. System administrators should prioritize updating their kernel versions to include this fix, particularly in production environments where multiple network namespaces are utilized. The solution maintains backward compatibility while providing stronger memory safety guarantees through improved namespace isolation mechanisms.
The implementation follows established kernel security patterns for managing shared resources across multiple execution contexts, ensuring that object references remain valid during their intended usage period. This approach prevents the race conditions that could lead to memory corruption and provides a more robust foundation for netfilter operations in multi-namespace environments. The fix represents a standard defensive programming technique that addresses timing issues inherent in concurrent access patterns to shared kernel data structures.