CVE-2024-1085 in Linux
Summary
by MITRE • 01/31/2024
A use-after-free vulnerability in the Linux kernel's netfilter: nf_tables component can be exploited to achieve local privilege escalation.
The nft_setelem_catchall_deactivate() function checks whether the catch-all set element is active in the current generation instead of the next generation before freeing it, but only flags it inactive in the next generation, making it possible to free the element multiple times, leading to a double free vulnerability.
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Analysis
by VulDB Data Team • 02/22/2024
The vulnerability identified as CVE-2024-1085 represents a critical use-after-free condition within the Linux kernel's netfilter subsystem, specifically affecting the nf_tables component that manages network packet filtering rules. This flaw exists in the nft_setelem_catchall_deactivate() function which handles the deactivation of catch-all set elements during netfilter operations. The vulnerability stems from improper synchronization between current and next generations of set elements, creating a race condition that allows for unsafe memory management operations.
The technical implementation of this vulnerability occurs when the kernel processes set elements within the nf_tables framework. During normal operation, the nft_setelem_catchall_deactivate() function should verify that catch-all elements are properly deactivated before freeing memory resources. However, the function incorrectly checks the activation status against the current generation rather than the next generation, while simultaneously only marking elements as inactive in the next generation. This discrepancy creates a window where the same memory location can be freed multiple times, resulting in a double free condition that fundamentally compromises memory integrity.
This double free vulnerability presents significant operational risks as it can be exploited to achieve local privilege escalation within the Linux kernel environment. Attackers with local access can leverage this condition to manipulate kernel memory structures and potentially execute arbitrary code with elevated privileges. The exploitation requires local system access and knowledge of kernel memory management patterns, but the impact extends beyond typical local privilege escalation scenarios to potentially enable full system compromise. The vulnerability affects systems running Linux kernels that include the problematic nf_tables implementation and represents a serious threat to system integrity and security.
The recommended mitigation strategy involves upgrading the Linux kernel to a version that includes the fix for commit b1db244ffd041a49ecc9618e8feb6b5c1afcdaa7, which corrects the generation checking logic in the nft_setelem_catchall_deactivate() function. This fix ensures proper synchronization between current and next generations when determining element deactivation status, preventing the double free condition from occurring. System administrators should prioritize applying this update across all affected systems, particularly those running kernel versions that include the vulnerable nf_tables implementation. Organizations should also consider implementing additional monitoring and detection mechanisms to identify potential exploitation attempts and maintain comprehensive system integrity verification processes.
This vulnerability aligns with CWE-415, which describes double free conditions in software applications, and represents a classic example of improper resource management in kernel space. The ATT&CK framework categorizes this as a privilege escalation technique through kernel exploitation, specifically targeting the kernel's memory management subsystem. The nftables subsystem is commonly used in enterprise environments for network filtering and security policy enforcement, making this vulnerability particularly concerning for organizations relying on Linux-based network security implementations. The vulnerability demonstrates the critical importance of proper synchronization mechanisms in kernel-level code and highlights the potential for seemingly minor logic errors to create severe security implications.