Decreasing Vulnerabilities Seen in Red Hat Linux


As usual there’s been a flurry of activity in the cloud and DevOps security space recently. In case you missed it, a particularly painful flaw was found in Red Hat Enterprise Linux’s DHCP (Dynamic Host Configuration Protocol) service not long ago.

The bug specifically affects RHEL 6 and 7 (and derivative OS, Fedora 28, apparently). The CVE folks allocated the following ID to it in case you want to look it up: CVE-2018-1111. What’s important to note about this discovery is that DHCP (the service which asks a DHCP server for a (usually) temporary IP address and then binds it to one of the host’s network interfaces) is a sometimes forgotten cornerstone of our current tech stacks. Amazon’s EC2 for example shouts out to a DHCP server whenever an instance is spun up. As well as asking for an IP address, your servers will  usually pick up DNS servers from DHCP requests, too.

A descendant of BOOTP, a similar service from a time gone by, the pervasive DHCP bug is commonly used on your home networks, your mobile networks and beyond. According to Red Hat the bug affects the “dhclient”, in tandem with the “NetworkManager” daemon, and means that “A malicious DHCP server, or an attacker on the local network able to spoof DHCP responses, could use this flaw to execute arbitrary commands with root privileges on systems using NetworkManager and configured to obtain network configuration using the DHCP protocol.”

At first glance, this vulnerability might make the RHEL naysayers complain that there’s yet another security issue that only affects Red Hat and not other Linux flavors. And, that must therefore mean that the other distributions are better at securing their packages. However, they couldn’t be more wrong.

The commercial model that Red Hat Inc offer is based around supporting enterprises with their products, on a paid-for basis, along with some consultancy on top for good measure. They’ve been very successful and now their products are in use globally on many mission critical opensource server estates. Why is this relevant? Well, aside from the fact that the (free) CentOS Linux flavour benefits from the downstream improvements made by Red Hat, the community as a whole does in addition.

I normally find that it’s hard to know who to believe when a lofty claim is made in the relatively congested Internet giants’ space,  However, a report published in November 2017 — called “The State of Open Source Security” — shows some evidence that Red Hat’s Linux might be ruling the roost for security currently. Obviously, I can’t make any guarantees for the report’s impartiality.

Commissioned by Snyk, the report states: “Open source library vulnerabilities increased by 53.8% in 2016, while Red Hat Linux vulnerabilities have decreased.” The report is well-constructed and easy to digest and, as a plumb line to what’s going on the with security on the Internet in general, it’s a welcome read. It states that there’s been a “65% decrease in Red Hat vulnerabilities since 2012” and in addition to that: “In 2016, 69% of Red Hat Linux vulnerabilities were fixed within a day of their public disclosure, and 90% were fixed within 14 days of their public disclosure”.

The report continues: “Red Hat Linux seems to be finding some level of stability” and “…it does make us optimistic that better security is achievable with a little bit of work”.

The truth, of course, is that every device or service has a vulnerability of some description or another, and, as the report states, “there are a lot of steps involved in the lifecycle of an open source security vulnerability. From discovery through final adoption of fixes, each part of the process is important in its own way, and ultimately plays a role in the overall state of security.” Code auditing is key as well as timely response to vulnerabilities. Check out the report to learn more.

Chris Binnie’s latest book, Linux Server Security: Hack and Defend, shows how hackers launch sophisticated attacks to compromise servers, steal data, and crack complex passwords. In the book, he also shows you how to make your servers invisible, perform penetration testing, and mitigate unwelcome attacks. You can find out more about DevOps, DevSecOps, Containers, and Linux security on his website: