TCP SACK Panic Flaw Could Compromise Production Linux Machines

A kernel flaw dubbed TCP SACK Panic could allow remote attackers to compromise organizations running large fleets of production Linux computers, according to a series of security advisories.

Netflix was among the first to raise alarm bells over the vulnerability, also known as CVE-2019-11477, which could potentially be used to crash a machine by triggering a kernel “panic.” The issue affects those running systems based on Linux kernel version 2.6.29 and above and is one of four known flaws. TCP SACK Panic is considered the most dangerous, researchers said.

The Scope of the SACK Panic Threat

In its own security advisory, Red Hat suggested that while the flaw could be used by cybercriminals to wage denial-of-service (DoS) attacks, it would not allow them to escalate privileges on compromised machines to steal information.

SACK refers to Selective Acknowledgment, a mechanism that has traditionally been used in Linux-based systems to ensure networks run efficiently even if there is TCP packet loss between senders and receivers. When the Socket Buffer (SKB) — a data structure within Linux TCP implementations — reaches more than 17 fragments of packet data, however, a kernel panic can cause it to crash.

Threat actors could also send specially crafted SACK packets that trigger a panic, researchers said, adding that all four of the reported flaws are interrelated. Others include SACK Slowness, also known as CVE-2019-11478, a resource consumption bug dubbed CVE-2019-11479, and another SACK slowness flaw known as CVE-2019-5599.

Stay Calm Amid the TCP SACK Panic

Flaws such as these can be addressed through software patches, but the onus is on those running vulnerable IT systems to ensure they are properly applied. Unfortunately, this doesn’t always happen as quickly and consistently as it should.

Experts have shown, for example, that many organizations would benefit from improved patch posture reporting. In other words, firms need a way to bring together all available data on what patches have been performed and whether they have remediated vulnerabilities. Tools are available to assist in this area, which may be the best way for Linux users to ensure they aren’t compromised by something like the TCP SACK Panic threat.

Shane Schick

Writer & Editor

NIST’s role in the global tech race against AI

4 min read - Last year, the United States Secretary of Commerce announced that the National Institute of Standards and Technology (NIST) has been put in charge of launching a new public working group on artificial intelligence (AI) that will build on the success of the NIST AI Risk Management Framework to address this rapidly advancing technology.However, recent budget cuts at NIST, along with a lack of strategy implementation, have called into question the agency’s ability to lead this critical effort. Ultimately, the success…

Researchers develop malicious AI ‘worm’ targeting generative AI systems

2 min read - Researchers have created a new, never-seen-before kind of malware they call the "Morris II" worm, which uses popular AI services to spread itself, infect new systems and steal data. The name references the original Morris computer worm that wreaked havoc on the internet in 1988.The worm demonstrates the potential dangers of AI security threats and creates a new urgency around securing AI models.New worm utilizes adversarial self-replicating promptThe researchers from Cornell Tech, the Israel Institute of Technology and Intuit, used what’s…

Passwords, passkeys and familiarity bias

5 min read - As passkey (passwordless authentication) adoption proceeds, misconceptions abound. There appears to be a widespread impression that passkeys may be more convenient and less secure than passwords. The reality is that they are both more secure and more convenient — possibly a first in cybersecurity.Most of us could be forgiven for not realizing passwordless authentication is more secure than passwords. Thinking back to the first couple of use cases I was exposed to — a phone operating system (OS) and a…

Security Intelligence

{{title}}

{{title}}

{{title}}

Topics

The Scope of the SACK Panic Threat

Stay Calm Amid the TCP SACK Panic

More from

NIST’s role in the global tech race against AI

Researchers develop malicious AI ‘worm’ targeting generative AI systems

Passwords, passkeys and familiarity bias

Topic updates