CVE-2026-64094 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
batman-adv: bla: avoid NULL-ptr deref for claim via dropped interface
Without rtnl_lock held, a hardif might be retrieved as primary interface of a meshif, but then (while operating on this interface) getting decoupled from the mesh interface. In this case, the meshif still exists but the pointer from the primary hardif to the meshif is set to NULL.
The mesh_iface must be checked first to be non-NULL before continuing to send an ARP request using meshif.
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Analysis
by VulDB Data Team • 07/19/2026
This vulnerability exists within the batman-adv kernel module, which implements the B.A.T.M.A.N. advanced routing protocol for wireless mesh networks. The issue manifests as a NULL pointer dereference that occurs during the processing of claim messages when interfaces are being dropped from the mesh network. The root cause stems from improper synchronization mechanisms where the rtnl_lock is not held during critical operations, creating a race condition between interface retrieval and interface detachment processes.
The technical flaw emerges when a hard interface is temporarily retrieved as the primary interface of a mesh interface but subsequently gets decoupled from the mesh while operations are still in progress. During this window, the system maintains a reference to the mesh interface through the primary hard interface's pointer, but this pointer gets set to NULL when the interface detachment occurs. This creates a scenario where subsequent operations attempt to dereference a NULL pointer that should have been validated before use.
The operational impact of this vulnerability is significant as it can lead to kernel crashes and system instability, particularly in environments running wireless mesh networks that utilize batman-adv for routing. The vulnerability affects the claim processing mechanism which is fundamental to maintaining network topology information in mesh networks. When triggered, the NULL pointer dereference causes immediate kernel panics, resulting in service disruption and potential data loss.
The vulnerability can be classified under CWE-476 as a NULL Pointer Dereference, and it aligns with ATT&CK technique T1547.001 related to Kernel Modules for privilege escalation opportunities. The race condition pattern suggests this could potentially be exploited for denial of service attacks against mesh network infrastructure. Mitigation strategies should focus on proper locking mechanisms around interface operations, ensuring that the mesh interface pointer is validated before any subsequent operations are performed.
Effective remediation requires implementing proper synchronization using rtnl_lock or equivalent kernel locking primitives to prevent concurrent access patterns that lead to inconsistent state. The code path must be modified to check for NULL mesh interface pointers immediately upon interface retrieval, preventing the execution flow from proceeding with invalid references. Additionally, defensive programming practices should be enforced throughout the batman-adv module to validate all pointer references before dereferencing them in critical sections.
The fix approach involves ensuring that when retrieving a mesh interface through a primary hard interface, proper validation occurs to confirm the mesh interface is still valid and accessible. This validation must occur before any ARP request or other operations are initiated using the mesh interface reference. The solution pattern should be consistent with kernel development best practices for handling concurrent data structures and should be reviewed against established patterns for similar race condition fixes in the Linux kernel codebase.
This vulnerability demonstrates the importance of careful synchronization in kernel modules where multiple threads or processes might access shared data structures concurrently. The fix represents a classic example of defensive programming that prevents null pointer dereferences through proper validation before resource usage, which is essential for maintaining kernel stability and preventing potential exploitation by malicious actors targeting mesh network infrastructure.