CVE-2026-98354 in Linux
Summary
by MITRE • 10/06/2026
In the Linux kernel, the following vulnerability has been resolved:
RDMA/mad: Fix receive buffer leak when PKey enforcement fails
ib_mad_complete_recv() initializes mad_recv_wc->rmpp_list and then runs ib_mad_enforce_security() before linking recv_buf onto that list. On failure it calls ib_free_recv_mad(), which only walks rmpp_list and frees the ib_mad_private of every buffer found there. As the list is still empty at that point, nothing is freed at all.
The caller cannot clean up either: ib_mad_recv_done() sets recv to NULL right after ib_mad_complete_recv() returns, assuming the MAD layer took ownership of the buffer. Every MAD that fails the PKey check therefore leaks one ib_mad_private (about 300 bytes per IB port MAD, ~2K for OPA), and a remote node can trigger this repeatedly by sending MADs with a wrong PKey.
Link recv_buf onto rmpp_list right after the list is initialized, so the error path has something to free.
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Analysis
by VulDB Data Team • 10/06/2026
The Linux kernel contains a resource management flaw within the Remote Direct Memory Access (RDMA) Management Information Base layer that results in memory leaks when packet key enforcement fails during message processing. This vulnerability specifically affects the ib_mad_complete_recv function, which is responsible for handling incoming MADs and ensuring they comply with security policies before being processed further by higher-level subsystems. The core issue stems from an incorrect ordering of operations regarding list initialization and buffer linkage. Specifically, the code initializes the rmpp_list structure but delays linking the receive buffer to this list until after a security check is performed. This sequencing error creates a critical gap in resource tracking during failure scenarios.
When ib_mad_enforce_security determines that a received MAD does not satisfy PKey enforcement requirements, it returns an error status. The execution flow then proceeds to call ib_free_recv_mad() to release the associated resources. However, because the receive buffer was never added to the rmpp_list prior to this failure check, the free function finds an empty list and consequently fails to deallocate any memory. This results in a direct leak of one ib_mad_private structure per failed MAD transaction. Given that each IB port MAD consumes approximately 300 bytes and OpenFabrics Alliance messages can consume up to two kilobytes, these leaks accumulate rapidly under sustained traffic conditions.
The operational impact of this vulnerability is significant due to the ease with which it can be triggered remotely. An attacker or a misconfigured remote node can repeatedly send MADs with incorrect PKeys to an affected system. Since each failed attempt results in unfreed kernel memory, continuous transmission leads to progressive exhaustion of available kernel memory resources. This constitutes a denial-of-service condition where legitimate services may become unresponsive due to resource starvation. The vulnerability is particularly dangerous because the caller function ib_mad_recv_done assumes that ownership of the buffer has been transferred to the MAD layer upon return from ib_mad_complete_recv, setting its local pointer to NULL and thereby relinquishing any ability to perform cleanup on behalf of the failed operation.
From a classification perspective, this flaw aligns with CWE-401, which describes missing release of memory after successful allocation, as well as CWE-789, concerning memory leaks that can lead to denial-of-service conditions. In terms of adversarial tactics, this vulnerability supports ATT&CK technique T1496, Resource Hijacking, where an attacker consumes system resources to degrade performance or cause a crash. The exploitation vector is network-based, allowing remote attackers without prior authentication to trigger the condition if they can reach the RDMA interface and send malformed PKey packets.
The resolution involves correcting the control flow within ib_mad_complete_recv by linking the recv_buf onto the rmpp_list immediately after list initialization but before executing the security enforcement check. This ensures that regardless of whether the PKey validation succeeds or fails, the buffer remains tracked in a data structure that is properly traversed during cleanup routines. By guaranteeing that every allocated receive buffer has an entry in the tracking list prior to potential failure paths, the ib_free_recv_mad function can correctly identify and deallocate all associated memory structures. This fix eliminates the leak path entirely while maintaining the intended security posture of PKey enforcement.
System administrators should apply kernel updates containing this patch as soon as possible, particularly for systems exposed to untrusted RDMA networks or environments where remote nodes may not be fully trusted. Monitoring kernel memory usage and looking for signs of gradual degradation in network service responsiveness can help identify affected systems prior to patching. Additionally, implementing strict firewall rules to restrict access to RDMA management ports from unauthorized sources provides a compensating control that limits the attack surface available to potential exploiters attempting to trigger this resource exhaustion condition.