Phoenix Attack Breaks DDR5 Rowhammer Defenses: Root in 109 Seconds

Daily Security Review

The infamous Rowhammer vulnerability, long thought to be contained by new DRAM protections, has resurfaced with devastating force. Academic researchers, working with Google, have unveiled the Phoenix attack, a breakthrough Rowhammer variant that shatters the defenses of DDR5 memory chips. Despite the industry’s investment in Target Row Refresh (TRR) and Error Correcting Codes (ECC), Phoenix exploits “blind spots” in SK Hynix DDR5 DIMMs—the world’s leading DRAM manufacturer—using novel hammering patterns and a self-correcting synchronization technique. In real-world tests, Phoenix achieved privilege escalation in as little as 109 seconds, giving attackers full root access on commodity DDR5 systems.

The implications are staggering: Phoenix enables arbitrary memory access via page-table entry manipulation, compromises cryptographic keys like RSA-2048 in SSH, and even tampers with system binaries such as sudo. Beyond immediate system exploits, clustered bit flips open the door to new attack vectors, from recovering private keys in OpenSSL to corrupting tokenizer dictionaries in large language models—potentially disabling AI safety guardrails.

The attack, assigned CVE-2025-6202, underscores the inadequacy of probabilistic defenses like TRR. AMD has issued BIOS updates in response, but effectiveness remains unverified. Google, meanwhile, is advocating for a more principled solution: the Per Row Activation Counting (PRAC) standard for DDR5 and LPDDR6, offering deterministic protection against hammering patterns.

Phoenix is more than a vulnerability—it’s a wake-up call for the memory industry. With 36% of the global DRAM market impacted and escalating risks to cryptographic integrity and AI systems, the need for robust, future-proof defenses has never been more urgent.

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