CVE-2024-26809 in Linux
Summary
by MITRE • 04/04/2024
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nft_set_pipapo: release elements in clone only from destroy path
Clone already always provides a current view of the lookup table, use it to destroy the set, otherwise it is possible to destroy elements twice.
This fix requires:
212ed75dc5fb ("netfilter: nf_tables: integrate pipapo into commit protocol")
which came after:
9827a0e6e23b ("netfilter: nft_set_pipapo: release elements in clone from abort path").
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Analysis
by VulDB Data Team • 08/05/2025
The vulnerability identified as CVE-2024-26809 affects the Linux kernel's netfilter subsystem, specifically within the nft_set_pipapo implementation that handles packet classification and filtering operations. This issue stems from improper memory management during set destruction operations within the nf_tables framework, creating a potential double-free condition that could lead to system instability or privilege escalation. The flaw manifests when the kernel attempts to clean up set elements during network packet filtering operations, where concurrent access patterns and memory management routines interact in unexpected ways.
The technical root cause involves the pipapo (prefix intersection and path aggregation) set implementation within the netfilter subsystem, which uses a clone mechanism to maintain current views of lookup tables for efficient packet processing. The vulnerability occurs because the system attempts to release set elements from multiple code paths, specifically from both the abort and destroy paths of the commit protocol. This duplication of cleanup operations creates a scenario where elements may be freed twice, leading to memory corruption and potential exploitation. The issue is particularly concerning because it affects the core packet filtering infrastructure that many network security policies depend upon.
The operational impact of this vulnerability extends beyond simple memory corruption, as it could enable attackers to exploit the double-free condition for privilege escalation or denial of service attacks. When the kernel's netfilter subsystem processes packets through nftables rules that utilize pipapo sets, the corrupted memory state could allow malicious actors to execute arbitrary code with kernel privileges. The vulnerability affects systems running Linux kernels that incorporate the specific commit protocol changes referenced in the fix, particularly those that have integrated the pipapo implementation into the nf_tables framework. This makes it a significant concern for network infrastructure devices, firewalls, and systems relying heavily on netfilter-based packet filtering.
The mitigation strategy involves applying the kernel patch that ensures elements are only released from the destroy path rather than from both abort and destroy paths, maintaining consistency with the current clone view of lookup tables. This fix aligns with secure coding practices that prevent double-free vulnerabilities, which are classified as CWE-415 in the Common Weakness Enumeration catalog and fall under the ATT&CK technique T1068 for exploit development through privilege escalation. Organizations should prioritize kernel updates to address this vulnerability, as the fix directly resolves the memory management inconsistency that enables potential exploitation. The patch implementation demonstrates proper resource management practices that prevent concurrent access issues in multi-threaded kernel subsystems, ensuring that cleanup operations occur only once per element regardless of the transaction outcome.