RAMBleed is a new Rowhammerbased side-channel attack that enables an attacker to read out the physical memory associated with the other process.

Academic researchers Andrew Kwong and Daniel Genkin from the University of Michigan, Daniel Gruss form Graz University and Yuval Yarom from University of Adelaide and Data 61 disclosed the attack method.

The RAMBleed attack is based on the previous Rowhammer attack, which lets the attacker flip the bit’s in the memory space of another process.

Rowhammer is a readability issue in DRAM that enables an attacker to flip bits in the memory space of other processes. “We show in our paper that an attacker, by observing Rowhammer-induced bit flips in her memory, can deduce the values in nearby DRAM rows.”

The RAMBleed shifts that Rowhammer is not only a threat by integrity but also a threat in confidentiality level as well. Like ROwhammer it doesn’t require any flip bits, so it is effective against ECC memory commonly used by server computers.

By exploiting the vulnerability, attackers can retrieve any data stored in the computer’s physical memory. To demonstrate, researchers presented an end-to-end attack on OpenSSH 7.9 that extracts an RSA-2048 key from the root level SSH daemon.

RAMBleed exploits a physical phenomenon in DRAM DIMMs wherein the likelihood of a Rowhammer induced bit flip depends on the values of the bits immediately above and below it.

Any system that uses Rowhammer-susceptible DIMMs is vulnerable to RAMBleed attack. According to researchers may classes of computers vulnerable are to RAMBleed.

The positive sign is that the attack was not exploited in the wild, and the vulnerability can be tracked as CVE-2019-0174.

RAMBleed Mitigations

Users are recommended to upgrade with memory to DDR4 with targeted row refresh (TRR) enabled.

Manufacturers can mitigate the issue by more rigorously testing for faulty DIMMs.

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