CVE-2026-53057: Linux RISC-V IOMMU Cache Invalidation Vulnerability – Local Privilege Escalation Risk

Technical summary

The Linux kernel's RISC-V IOMMU implementation has a flaw in how it manages device directory table (DDT) and page directory table (PDT) entry updates. According to the RISC-V IOMMU specification (Sections 6.3.1 and 6.3.2), updates to DDT or PDT entries must be followed by explicit TLB and context cache invalidation operations to ensure coherency. The vulnerability arises from the absence of the riscv_iommu_iodir_iotinval() function call after these updates, leaving stale translations cached in the IOMMU. A local unprivileged user can exploit this to access memory regions that should be isolated, potentially reading or modifying data belonging to other processes or the kernel, or degrading I/O device isolation guarantees.

Business impact

For organizations running Linux on RISC-V-based systems (particularly embedded, IoT, or specialized computing environments), this vulnerability undermines the security isolation mechanisms that the IOMMU provides between processes and devices. Affected deployments could experience unauthorized data access, privilege escalation within the system, or crashes due to corrupted IOMMU state. In multi-tenant or security-sensitive RISC-V deployments, this directly increases the risk of lateral movement and data breach. The vulnerability particularly concerns vendors and integrators building RISC-V-based products where guest isolation or process containment is a security requirement.

Affected systems

The vulnerability affects the Linux kernel's RISC-V IOMMU driver. It impacts systems running Linux on RISC-V processors that rely on the IOMMU for address translation and device isolation. Deployments using RISC-V SoCs (System-on-Chip) in embedded systems, edge computing, or data center environments where the kernel RISC-V IOMMU support is enabled are at risk. The fix is kernel-version dependent; affected versions are those released before the patch was integrated. Verify your kernel version and RISC-V IOMMU driver status to determine exposure.

Exploitability

The attack requires local access to the system and the ability to execute code as an unprivileged user (no root or IOMMU-specific permissions needed). The accessibility is straightforward for any user account on the system. Exploitation does not require network access, complex race conditions, or specialized hardware—only the ability to manipulate memory or trigger IOMMU operations through normal system interfaces. The relatively low barrier to entry combined with the high impact makes this a moderate-to-high exploitability concern in multi-user or containerized environments, though actual weaponization depends on RISC-V ecosystem maturity and the specific system configuration.

Remediation

Apply a kernel update that includes the fix adding riscv_iommu_iodir_iotinval() calls to the DDT and PDT update code paths. Verify against the vendor's official Linux kernel advisory and your distribution's security bulletins for the patched kernel version applicable to your RISC-V platform. As an interim mitigation, restrict local user access on systems where RISC-V IOMMU isolation is a critical security control, though this does not eliminate the risk. Kernel rebuilds incorporating the upstream fix are recommended if distribution patches are not yet available.

Patch guidance

Monitor official Linux kernel repositories and your Linux distribution's security advisories for patches addressing this vulnerability. The fix adds the missing IOTINVAL invalidation function. Apply kernel updates as soon as they are available and tested in your environment. Verify that the patched kernel version explicitly includes fixes for the RISC-V IOMMU DDT/PDT update paths. Test thoroughly in a staging environment before production deployment, as kernel updates require system reboot and may interact with IOMMU-dependent drivers or firmware.

Detection guidance

Monitor kernel logs for signs of IOMMU-related errors, stale TLB entries, or unexpected memory access violations that may indicate exploitation attempts. In RISC-V-specific debug environments, enable IOMMU-level tracing to detect misaligned DDT/PDT updates or missing invalidation operations. System behavior such as process isolation failures, cross-process memory leaks, or I/O device access violations may indicate active exploitation. Intrusion detection systems should flag unexpected privilege escalation or unauthorized device memory access from unprivileged processes. Direct detection of the vulnerability state (before exploitation) requires kernel source inspection or runtime verification of cache coherency behavior.

Why prioritize this

Despite not yet being tracked in the KEV catalog, this vulnerability merits immediate attention due to its HIGH CVSS score (8.8), local privilege escalation potential, and impact on system memory isolation guarantees. The RISC-V ecosystem, though smaller than x86/ARM, is rapidly expanding in critical IoT, edge, and specialized computing domains. Any organization with RISC-V deployments where security isolation is important should prioritize patching. The vulnerability's alignment with the RISC-V specification gap increases the likelihood of similar issues across multiple RISC-V IOMMU implementations, amplifying collective risk.

Risk score, explained

The CVSS 3.1 score of 8.8 (HIGH) reflects: local attack vector (AV:L) limiting initial access to system users; low attack complexity (AC:L) requiring no special conditions; low privilege requirement (PR:L) needing only unprivileged user status; no user interaction (UI:N); changed scope (S:C) affecting beyond the IOMMU driver itself; and high impact across confidentiality (C:H), integrity (I:H), and availability (A:H). The score appropriately captures that a low-privileged local user can compromise memory isolation and system stability without sophisticated techniques.

Frequently asked questions