CVE-2026-68419 in Linux
Summary
by MITRE • 08/10/2026
In the Linux kernel, the following vulnerability has been resolved:
RDMA/irdma: Prevent rereg_mr for non-mem regions
When a QP/CQ/SRQ is created, a two step process is used where the buffer is allocated in userspace and explicitly registered with the normal reg_mr mechanism prior to creating the actual QP/CQ/SRQ object.
These special registrations are indicated via an ABI field so the driver knows that they do not have a valid mkey and to skip the actual CQP command submission.
Since these are real MR objects from the core's perspective, it is possible for a user application to invoke rereg_mr on them and cause a real CQP op to be emitted with the zero-initialized mkey value of 0.
Fix this by preventing rereg_mr on these special regions.
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Analysis
by VulDB Data Team • 08/10/2026
This vulnerability exists within the Linux kernel's RDMA implementation, specifically affecting the irdma driver component that handles InfiniBand and RoCE communications. The issue stems from a design flaw in how memory regions are managed during the creation of Queue Pairs, Completion Queues, and Solicited Response Queues. When these network objects are instantiated, the system employs a two-step registration process where userspace allocates buffers first and then registers them using the standard reg_mr mechanism before finalizing the QP/CQ/SRQ object creation. The kernel maintains an Application Binary Interface field to identify these special registration cases that should not proceed through normal hardware command submission processes since they lack valid memory keys.
The technical flaw occurs because these special memory regions, while marked as non-hardware objects from the driver's perspective, are still recognized as legitimate memory region objects by the kernel's core memory management subsystem. This creates an exploitable condition where user applications can invoke the rereg_mr (re-register memory region) operation on these special objects, which bypasses the normal validation checks that should prevent hardware command submission. When rereg_mr is executed on these artificial regions, the system attempts to submit a real CQP (Command Queue Pair) operation using a zero-initialized mkey value of 0, effectively causing an invalid hardware operation that could lead to system instability or potential privilege escalation.
The operational impact of this vulnerability extends beyond simple system crashes, potentially allowing malicious users to manipulate the RDMA subsystem in ways that could compromise system integrity. This flaw particularly affects systems utilizing InfiniBand and RoCE networking where RDMA operations are common, creating opportunities for attackers to exploit the memory management inconsistency between userspace and kernel-space operations. The vulnerability represents a classic case of improper access control and validation within kernel memory management, where objects that should be restricted from certain operations are not properly protected from user-space manipulation.
The fix implemented addresses this by explicitly preventing rereg_mr operations on these special memory regions through kernel code modifications that check for the special registration flag before allowing any re-registration attempts. This approach aligns with security best practices outlined in CWE-691, which addresses insufficient control of a resource through a public interface, and follows ATT&CK technique T1068 by preventing privilege escalation through kernel exploits. The mitigation strategy ensures that memory regions flagged as special during the initial registration process cannot be subsequently modified through user-space operations, thereby maintaining the integrity of the hardware command submission process while preserving legitimate functionality for normal memory regions. This solution demonstrates proper defense-in-depth principles where multiple layers of protection prevent unauthorized access to critical system resources.
The vulnerability highlights a broader class of issues in kernel memory management where special objects that should be restricted from certain operations are not properly isolated from user-space manipulation, creating potential attack vectors through improper validation of memory region operations.