DDRop: Active Memory Interposer Attacks on Confidential VMs by Dropping DDR5 Writes

Trusted Execution Environments (TEEs) are increasingly deployed in the cloud to protect sensitive workloads through hardware-enforced isolation, remote attestation, and transparent memory encryption. However, to meet memory performance and size demands , modern TEEs omit cryptographic freshness guarantees, leaving them vulnerable to replay attacks by adversaries with physical memory access. Prior work demonstrated low-cost active inter-position attacks on DDR4 without requiring expensive specialized equipment, but these techniques do not extend to DDR5, where existing approaches are limited to passive ciphertext side-channel analysis and rely on bus downclocking to accommodate legacy memory bus analyzers. We present the first low-cost (<200$) DDR5 RDIMM interposer capable of active fault injection at native speeds. By injecting targeted parity errors to silently discard cache line writebacks, we introduce DDRop, a new primitive that exploits the absence of cryptographic freshness to break the integrity of Intel TDX, Scalable SGX, and AMD SEV-SNP. Building on this primitive and targeting the APIs exposed by the TDX module and AMD Secure Processor, we show that adversaries can gain ciphertext access, copy arbitrary victim pages, and inject malicious secure page-table entries. We demonstrate end-to-end attacks on an up-to-date TDX platform, including forcing any TD into debug mode and forging attestation reports. While software-level mitigations, including timing-based interposer detection and API hardening, may reduce the attack surface , our results demonstrate that active DDR5 bus interposition is practical at low cost, highlighting the need for robust cryptographic memory integrity protections against physical adversaries. This work is licensed under a Creative Commons Attribution 4.0 International License. CCS '26, • Security and privacy → Hardware attacks and countermeasures .