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University of Toronto researchers disclosed GPUThor, a GPU-based Rowhammer technique that can bypass practical protections provided by SECDED ECC on certain NVIDIA Ampere workstation GPUs using GDDR6 memory, including the RTX A6000. By using a non-uniform memory-hammering pattern that accounts for undocumented request coalescing and Target Row Refresh behavior, the technique substantially increases bit-flip rates and can trigger uncorrectable double-bit errors or incorrect repair of triple-bit errors.
An attacker needs to execute an unprivileged CUDA kernel, creating risk in shared GPU-tenancy environments and from untrusted local GPU workloads. The researchers demonstrated data corruption and GPU denial of service and described a path to host root privilege escalation through GPU page-table corruption. NVIDIA recommends enabling System-Level ECC (SYS-ECC), enforcing IOMMU/DMA isolation, monitoring GPU ECC telemetry, and restricting untrusted or cross-tenant GPU workloads; no CVE, patch, or confirmed in-the-wild exploitation was reported.
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The GPUThor vulnerability disclosure embargo ended. The researchers stated that no patch or CVE had been issued for the technique.
NVIDIA published an advisory with mitigations for GPUThor, including enabling system-level ECC and IOMMU/DMA isolation, monitoring GPU error telemetry, and restricting untrusted or shared GPU workloads.
University of Toronto researchers reported the GPUThor Rowhammer technique to NVIDIA and notified Google, Microsoft, and AWS. The issue affects certain Ampere-class NVIDIA GPUs with GDDR6 memory and can induce multi-bit errors despite SECDED ECC.
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University of Toronto researchers described **GPUThor**, a Rowhammer-class attack targeting GDDR6 memory in NVIDIA Ampere GPU accelerators. The technique characterizes the platform’s Targeted Refresh Rate (TRR) behavior and uses non-uniform memory-access patterns to induce substantially more bit flips than earlier GPU Rowhammer methods, extending the DRAM disturbance-error threat first established by Rowhammer research. GPUThor generated double- and triple-bit memory corruptions, which can exceed ECC’s single-bit correction capability. Researchers demonstrated a denial-of-service outcome: a GPU reset accompanied by data loss and a hardware-replacement warning. They did not demonstrate arbitrary code execution or compromise newer GPU generations; ECC bypass leading to code execution remains theoretical.
Sep 8, 2026
Researchers disclosed two GPU-based Rowhammer techniques, **`GDDRHammer`** and **`GeForge`**, that can induce bit flips in GDDR6 VRAM on certain Nvidia GPUs and break memory isolation. Tests showed the attacks against Ampere-era cards including the **RTX 3060** and **RTX A6000/RTX 6000**, where corrupted GPU page tables or page directories allowed attackers to gain read/write access to protected VRAM regions and, in some cases, remap access into host memory. The researchers said this could escalate from GPU compromise to **full control of the machine**, including root-level access to system memory. The reports said the attacks require an adversary to already run code on the target system, making shared GPU environments such as AI clusters a more plausible risk than a purely remote attack path. No in-the-wild exploitation has been reported, but the findings highlight a hardware security gap in systems where GPUs can directly access host memory. Recommended mitigations include enabling **IOMMU** in BIOS to restrict device DMA access to sensitive system memory and turning on **ECC** on supported GPUs, though both measures can impose performance or memory-capacity tradeoffs and ECC may not block every Rowhammer variant.
Jun 29, 2026
Researchers reported that **Rowhammer** remains a practical hardware security threat, with the newer **Phoenix** technique showing that **DDR5** memory can still be manipulated despite built-in protections. The attack revives a flaw first highlighted by Google Project Zero, which demonstrated that repeatedly accessing DRAM rows could trigger adjacent bit flips and be weaponized for **privilege escalation** on x86 systems, including a Linux kernel exploit that altered page table entries and a sandbox escape from **Google Native Client**. The newer findings indicate that DDR5 mitigations have not eliminated the underlying risk, extending concerns that began with widespread **DDR3** exposure across tested laptop models. Earlier research had already shown Rowhammer was more than a reliability issue, and the latest reports suggest modern memory modules remain susceptible to carefully engineered disturbance attacks that can undermine isolation boundaries and system integrity, renewing pressure on hardware vendors to disclose affected products and strengthen defenses.
Jun 29, 2026