CVE-2021-42114

Technical Description

Modern DRAM devices (PC-DDR4, LPDDR4X) are affected by a vulnerability in their internal Target Row Refresh (TRR) mitigation against Rowhammer attacks. Novel non-uniform Rowhammer access patterns, consisting of aggressors with different frequencies, phases, and amplitudes allow triggering bit flips on affected memory modules using our Blacksmith fuzzer. The patterns generated by Blacksmith were able to trigger bitflips on all 40 PC-DDR4 DRAM devices in our test pool, which cover the three major DRAM manufacturers: Samsung, SK Hynix, and Micron. This means that, even when chips advertised as Rowhammer-free are used, attackers may still be able to exploit Rowhammer. For example, this enables privilege-escalation attacks against the kernel or binaries such as the sudo binary, and also triggering bit flips in RSA-2048 keys (e.g., SSH keys) to gain cross-tenant virtual-machine access. We can confirm that DRAM devices acquired in July 2020 with DRAM chips from all three major DRAM vendors (S

Remediation

Check the references section for vendor advisories and patches from samsung. Update ddr4_sdram_firmware to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

Affected Products

References