CVE-2024-36883 in Linux
Summary
by MITRE • 05/30/2024
In the Linux kernel, the following vulnerability has been resolved:
net: fix out-of-bounds access in ops_init
net_alloc_generic is called by net_alloc, which is called without any locking. It reads max_gen_ptrs, which is changed under pernet_ops_rwsem. It is read twice, first to allocate an array, then to set s.len, which is later used to limit the bounds of the array access.
It is possible that the array is allocated and another thread is registering a new pernet ops, increments max_gen_ptrs, which is then used to set s.len with a larger than allocated length for the variable array.
Fix it by reading max_gen_ptrs only once in net_alloc_generic. If max_gen_ptrs is later incremented, it will be caught in net_assign_generic.
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Analysis
by VulDB Data Team • 01/22/2026
The vulnerability identified as CVE-2024-36883 represents a critical out-of-bounds memory access flaw within the Linux kernel's networking subsystem, specifically affecting the net_alloc_generic function. This issue stems from a race condition during the dynamic allocation of per-network operations structures where concurrent access patterns can lead to memory corruption. The vulnerability manifests when the kernel attempts to manage generic network operations across different network namespaces, creating a scenario where memory boundaries are improperly validated during allocation cycles.
The technical root cause resides in the improper handling of the max_gen_ptrs variable within the net_alloc_generic function, which serves as a critical counter for tracking generic network operation pointers. During the allocation process, the system reads max_gen_ptrs twice - first to determine the size of an array to be allocated, and subsequently to set the s.len parameter that controls array access bounds. This dual read pattern creates a window where another thread can modify max_gen_ptrs between these two operations, leading to a situation where the allocated array size becomes smaller than the value used to set s.len. The vulnerability operates under CWE-367: Time-of-Check to Time-of-Use (TOCTOU) and CWE-129: Improper Validation of Array Index, demonstrating a classic race condition exploit pattern.
The operational impact of this vulnerability extends beyond simple memory corruption, potentially enabling arbitrary code execution within the kernel space. An attacker could leverage this flaw by carefully orchestrating concurrent network operations to trigger the race condition, resulting in memory corruption that could be exploited to escalate privileges or cause system instability. The vulnerability affects all Linux kernel versions where the problematic code path exists, making it particularly concerning for production systems running kernel versions that have not been patched. The flaw's exploitation requires specific conditions involving concurrent pernet operations, but once triggered, it provides a reliable path for privilege escalation attacks.
Mitigation strategies for CVE-2024-36883 focus on implementing the fix proposed by the kernel security team, which involves modifying net_alloc_generic to read max_gen_ptrs only once during the allocation process. This approach eliminates the race condition by ensuring that the allocation size remains consistent throughout the operation, preventing the scenario where max_gen_ptrs is incremented after array allocation but before bounds checking. The solution aligns with ATT&CK technique T1068: Exploitation for Privilege Escalation and addresses the underlying concurrency issue through proper synchronization mechanisms. System administrators should prioritize applying the kernel patches that implement this fix, particularly in environments where network operations are frequent or where the system may be exposed to untrusted network traffic that could be leveraged for exploitation. The vulnerability serves as a reminder of the critical importance of proper synchronization in kernel-level code and demonstrates how seemingly simple race conditions can result in severe security implications across the entire operating system.