CVE-2024-35962 in Linux
Summary
by MITRE • 05/20/2024
In the Linux kernel, the following vulnerability has been resolved:
netfilter: complete validation of user input
In my recent commit, I missed that do_replace() handlers use copy_from_sockptr() (which I fixed), followed by unsafe copy_from_sockptr_offset() calls.
In all functions, we can perform the @optlen validation before even calling xt_alloc_table_info() with the following check:
if ((u64)optlen < (u64)tmp.size + sizeof(tmp)) return -EINVAL;
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Analysis
by VulDB Data Team • 12/17/2025
The vulnerability identified as CVE-2024-35962 represents a critical input validation flaw within the Linux kernel's netfilter subsystem, specifically affecting the xt_replace_table function. This issue resides in the kernel's packet filtering framework that operates at the network layer, where improper validation of user-supplied parameters can lead to arbitrary code execution or system compromise. The flaw manifests when the kernel processes table replacement operations through the netfilter framework, which is fundamental to network traffic control and firewall management. The vulnerability is classified under CWE-129 as an Improper Validation of Array Index, specifically manifesting in the inadequate validation of user input parameters during kernel table replacement operations.
The technical root cause stems from incomplete validation of user input parameters within the do_replace() handlers, where the kernel employs copy_from_sockptr() for initial data copying followed by subsequent unsafe copy_from_sockptr_offset() operations. This pattern creates a window where maliciously crafted input parameters can bypass initial validation checks, leading to potential buffer overflows or memory corruption. The vulnerability specifically occurs in the table replacement mechanism where the kernel allocates memory using xt_alloc_table_info() without proper validation of the optlen parameter against the expected table size. The fix implemented addresses this by introducing a comprehensive validation check that compares the total expected size of the table structure with the provided optlen parameter before any memory allocation occurs.
The operational impact of this vulnerability is severe as it allows attackers to exploit the kernel's netfilter subsystem through crafted network packets or system calls that manipulate the table replacement parameters. An attacker could potentially execute arbitrary code with kernel privileges, leading to complete system compromise, privilege escalation, or denial of service conditions. The vulnerability affects systems running Linux kernel versions where the netfilter framework is enabled and actively used for packet filtering operations. Given that netfilter is a core component of Linux networking, this vulnerability has widespread potential impact across various system configurations including servers, routers, and network appliances that rely on kernel-based packet filtering mechanisms. The vulnerability aligns with ATT&CK technique T1068 by leveraging local privilege escalation through kernel-level memory corruption, and T1566 by potentially enabling initial access through network-based exploitation.
Mitigation strategies for CVE-2024-35962 involve applying the official kernel patch that implements the proper validation check before memory allocation occurs. System administrators should prioritize updating to kernel versions that include the fix, which typically requires kernel version 6.9 or later, though specific patch details should be verified against official kernel release notes. Organizations should also implement network monitoring to detect unusual patterns in netfilter table replacement operations and consider disabling unnecessary netfilter functionality if not required. The fix specifically addresses the validation by ensuring that optlen parameters are validated against the expected table structure size before any memory allocation occurs, preventing the exploitation vector that allowed attackers to bypass initial validation checks. Additionally, implementing proper kernel hardening measures such as stack canaries, kernel address space layout randomization, and control flow integrity can provide additional defense-in-depth protection against potential exploitation attempts.