June 23, 2019

SACK Attack | TechSNAP 406

43 minutes

A new vulnerability may be the next 'Ping of Death'; we explore the details of SACK Panic and break down what you need to know.

Plus Firefox zero days targeting Coinbase, the latest update on Rowhammer, and a few more reasons it's a great time to be a ZFS user.

Links:

SACK Panic Security Bulletin — Netflix has identified several TCP networking vulnerabilities in FreeBSD and Linux kernels. The vulnerabilities specifically relate to the Maximum Segment Size (MSS) and TCP Selective Acknowledgement (SACK) capabilities. The most serious, dubbed “SACK Panic,” allows a remotely-triggered kernel panic on recent Linux kernels.
Ubuntu SACK Panic Guidance — You should update your kernel to the versions specified below in the Updates section and reboot. Alternatively, Canonical Livepatch updates will be available to mitigate these two issues without the need to reboot.

Red Hat SACK Panic Advisory — Red Hat customers running affected versions of these Red Hat products are strongly recommended to update them as soon as errata are available. Customers are urged to apply the available updates immediately and enable the mitigations as they feel appropriate.

RFC 2018 - TCP Selective Acknowledgment Options — TCP may experience poor performance when multiple packets are lost from one window of data. With the limited information available from cumulative acknowledgments, a TCP sender can only learn about a single lost packet per round trip time. An aggressive sender could choose to retransmit packets early, but such retransmitted segments may have already been successfully received. A Selective Acknowledgment (SACK) mechanism, combined with a selective repeat retransmission policy, can help to overcome these limitations.

Ping of Death — In a nutshell, it is possible to crash, reboot or otherwise kill a large number of systems by sending a ping of a certain size from a remote machine.

Firefox zero-day was used in attack against Coinbase employees, not its users | ZDNet — A recent Firefox zero-day that has made headlines across the tech news world this week was actually used in attacks against Coinbase employees, and not the company's users.

Mozilla fixes second Firefox zero-day exploited in the wild | ZDNet — Mozilla has released a second security update this week to patch a second zero-day that was being exploited in the wild to attack Coinbase employees and other cryptocurrency organizations.

RAMBleed — RAMBleed is a side-channel attack that enables an attacker to read out physical memory belonging to other processes. The implications of violating arbitrary privilege boundaries are numerous, and vary in severity based on the other software running on the target machine. As an example, in our paper we demonstrate an attack against OpenSSH in which we use RAMBleed to leak a 2048 bit RSA key.

Digging into the new features in OpenZFS post-Linux migration | Ars Technica — One of the most important new features in 0.8 is Native ZFS Encryption. Until now, ZFS users have relied on OS-provided encrypted filesystem layers either above or below ZFS. While this approach does work, it presented difficulties.

Allan Jude on Twitter — Once the FreeBSDs are upstreamed, everything is changing to 'OpenZFS', including the github organization currently know as 'zfsonlinux'.

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