CVE-2026-53312

What it actually does

This flaw is an integer overflow in the Linux kernel RISC-V IOMMU invalidation path. When an invalidation range reaches a sign-extended page-table boundary such as ULONG_MAX, range handling can wrap instead of terminating correctly, causing the invalidation loop to run indefinitely. The practical technical result is denial of service through CPU lockup, kernel soft lockup, hung tasks, or loss of responsiveness on affected RISC-V systems using the RISC-V IOMMU code path.

Why it matters to the business

Successful exploitation can make affected RISC-V Linux systems unresponsive, interrupt workloads, and require a reboot or failover to restore service. The risk is currently lower than widely weaponized issues because there is no known CISA KEV listing, no known ransomware use, no public exploit maturity reported, and EPSS is low; however, systems that rely on RISC-V hardware, device passthrough, virtualization, or DMA-heavy workloads may experience material availability impact if the vulnerable path is reachable.

How an attack unfolds

An attacker must be able to cause the kernel to perform RISC-V IOMMU invalidation over a boundary condition where the invalidation end address can reach a value such as ULONG_MAX. This is most plausibly reached through local interaction with kernel facilities that create, modify, or tear down IOMMU mappings, such as device assignment, VFIO, virtualization, driver operations, or DMA mapping workflows. The attacker triggers a crafted or edge-case invalidation range; the vulnerable arithmetic overflows while computing or iterating the range; the kernel remains stuck in the invalidation loop; CPU time is consumed indefinitely; and the host or workload becomes degraded or unavailable. There is no indication from the provided data that this is remotely exploitable or that it enables code execution or privilege escalation.

How to fix it

Upgrade the Linux kernel to a version that includes the fix for the RISC-V IOMMU invalidation overflow. If consuming a vendor kernel, apply the relevant distribution, appliance, hypervisor, or embedded-platform kernel update when available rather than relying only on upstream version numbers. No exact fixed package versions were provided in the input, so remediation should be tracked through the operating-system or device vendor advisory for this CVE. Where immediate patching is not possible, reduce exposure by limiting access to local users and workloads that can exercise device passthrough, VFIO, DMA mapping, or RISC-V IOMMU functionality; disable unneeded device assignment; restrict untrusted workloads on affected hosts; and ensure HA/failover and watchdog reboot policies are in place for availability-sensitive systems.

How to confirm the fix worked

Confirm remediation by verifying that the running kernel package contains the upstream fix for the RISC-V IOMMU invalidation overflow, not merely that a patched package is installed on disk. Reboot into the updated kernel where required and verify with kernel package metadata, vendor advisory mapping, and runtime kernel version checks. Confirm whether the host is RISC-V and whether RISC-V IOMMU support is enabled or in use. For exposure validation, review kernel configuration, boot logs, loaded modules, device-passthrough configuration, and virtualization/VFIO usage. If safe in a controlled test environment, reproduce the relevant IOMMU invalidation boundary scenario before and after patching and confirm that the patched kernel completes invalidation without soft lockup or hang.

Typical attack path

1. Identify a RISC-V Linux system using the vulnerable RISC-V IOMMU implementation.
2. Obtain local access or control over a workload, driver interaction, VM/device-assignment path, or other interface capable of causing IOMMU map/unmap invalidations.
3. Trigger an IOMMU invalidation range that reaches the overflow-prone end-address boundary.
4. Cause the invalidation loop to wrap or fail to terminate.
5. Induce a kernel soft lockup, hung task condition, service outage, or required reboot.

How to detect it

There are no highly specific public exploitation artifacts in the provided data, and exploitation may leave only availability symptoms rather than a distinctive compromise trace. Review kernel logs, system journals, hypervisor logs, and crash/watchdog records for soft lockups, hung tasks, IOMMU invalidation messages, unexplained CPU stalls, or reboots around the time of suspected activity. Pay particular attention to events following VFIO operations, VM start/stop, device passthrough changes, driver unloads, DMA mapping failures, or workload actions that manipulate device mappings. On systems with audit or EDR telemetry, correlate local users, privileged containers, VM management actions, or device-assignment operations immediately preceding kernel hangs. Because this issue is a denial-of-service condition rather than a code-execution flaw, absence of files, processes, or network indicators does not rule out attempted exploitation.

• riscv_iommu
• iommu/riscv
• IOMMU
• VFIO
• vfio-pci
• DMA mapping
• IOTLB
• soft lockup
• BUG: soft lockup
• watchdog: BUG: soft lockup
• INFO: task hung
• blocked for more than
• RCU stall
• rcu_sched detected stalls
• NMI watchdog
• kernel panic - not syncing
• hung_task_timeout_secs

What your security team should do

• Prioritize inventory of RISC-V Linux systems, especially hosts using IOMMU, VFIO, device passthrough, virtualization, or DMA-heavy workloads.
• Apply vendor kernel updates that include the fix as part of the next maintenance window; accelerate patching for internet-facing management platforms, multi-tenant compute, or systems running untrusted local workloads.
• If patching is delayed, restrict local shell access, container privileges, VM device assignment, VFIO access, and direct hardware access to trusted administrators and workloads only.
• Monitor affected systems for kernel soft lockups, hung tasks, unexplained reboots, watchdog resets, or IOMMU-related errors.
• Ensure availability controls are in place, including watchdogs, clustering, workload failover, and tested reboot procedures for affected RISC-V hosts.
• Track vendor advisories because exact fixed versions were not provided, and downstream distributions may backport the fix without changing to a visibly new upstream kernel version.