Tag: advisory

Breaking
by Christopher Werny

CVE-2016-1409 – IPv6 NDP DoS Vulnerability in Cisco Software

Dear readers,

As you may have already noticed, Cisco released an urgent security advisory describing an IPv6 Neighbor Discovery DoS Vulnerability in several flavors of Cisco’s operating systems. Currently IOS-XR, XE and NX-OS are affected while ASA and “classic” IOS are under investigation. At first glance, it might look like yet another IPv6 DoS vulnerability. Looking closer, Cisco is mentioning an unauthenticated, remote attacker due to insufficient processing logic for crafted IPv6 NDP packets that are sent to an affected device. Following the public discussion about the vulnerability, it seems that these packets will reach the, probably low rate-limited, LPTS filter/queue on IOS XR devices “crowding” out legitimate NDP packets resulting in a DoS for IPv6 traffic, or in general a high CPU load as these packets will be processed by the CPU. More details are currently not available, but this might indicate the affected systems aren’t doing proper message validation checks on NDP packets (in addition to the LPTS filter/queue problem).

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Breaking
by Felix Wilhelm

Xen XSA 155: Double fetches in paravirtualized devices

As part of my research on the security of paravirtualized devices, I reported a number of vulnerabilities to the Xen security team, which were patched today. All of them are double fetch vulnerabilities affecting the different backend components used for paravirtualized devices. While the severity and impact of these bugs varies heavily and is dependent on a lot of external factors, I would recommend patching them as soon as possible. In the rest of this blog post I’ll give a short teaser about my research with full details coming out in the first quarter of 2016 .

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Breaking
by Matthias Luft

VMware did it again: vCenter Remote Code Execution

Yesterday 7Elements released the description of a Remote Code Execution vulnerability in VMware vCenter. The information came in at a good point as I’m at the moment drafting a follow-up blogpost for this one which will summarize some of our approaches to virtualization security. The vCenter vulnerability is both quite critical and particularly interesting in several ways:

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Breaking
by Felix Wilhelm

General Pr0ken Filesystem – Hacking IBM’s GPFS

This post is a short wrap-up of our Troopers talk about the research we did on IBM’s General Parallel File System. If you are interested in all the technical details take a look at our slides or the video recording. We will also give an updated version of this talk at the PHDays conference in Moscow next month.

The IBM General Parallel File System is a distributed file system used in large scale enterprise environments, high performance clusters as well as some of the worlds largest super computers. It is considered by many in the industry to be the most feature rich and production hardened distributed file system currently available. GPFS has a long and really interesting history, going back to the Tiger Shark file system created by IBM 1993.

Of course, this makes it an interesting target for security research. When looking at GPFS from an implementation point of view, the Linux version is made up of three different components: User space utilities and helper scripts, the mmfsd network daemon and multiple Linux kernel modules. We (Florian Grunow and me) spent some time analyzing the internals of these components and discovered critical vulnerabilities in all of them.

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Breaking
by Kevin Schaller

XML External Entity (XXE) Injection in Apache Batik Library [CVE-2015-0250]

During one of our latest web application code review projects I came across a vulnerability for which I think it is worth to speak about. It is an injection based attack against XML parsers which uses a rarely required feature called external entity expansion. The XML specification allows XML documents to define entities which reference resources external to the document and parsers typically support this feature by default. If an application parses XML input from untrusted sources and the parsing routine is not properly configured this can be exploited by an attacker with a so called XML external entity (XXE) injection. A successful XXE injection attack could allow an attacker to access the file system, cause a DoS attack or inject script code (e.g. Javascript to perform an XSS attack).
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Breaking
by Felix Wilhelm

Revisiting Xen’s x86 Emulation: Xen XSA 123

In my last blog post, I gave an overview about recent vulnerabilities discovered in the x86 emulation layer of Xen. While both of the discussed vulnerabilities only allow for guest privilege escalation, the complexity of the involved code seemed to indicate that even more interesting bugs could be discovered. So I spent some time searching for memory corruption issues and discovered a very interesting bug that resulted in XSA 123 . This post gives an overview about the root cause of the bug and a short description of exploitation challenges. A follow-up post will describe possible exploitation strategies in more detail.

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Breaking
by Felix Wilhelm

The Dangers of x86 Emulation: Xen XSA 110 and 105

Xen Logo

Developing a secure and feature rich hypervisor is no easy task. Recently, the open source Xen hypervisor was affected by two interesting vulnerabilities involving its x86 emulation code: XSA 110 and XSA 105. Both bugs show that the attack surface of hypervisors is often larger than expected. XSA 105 was originally reported by Andrei Lutas from BitDefender. The patch adds missing privilege checks to the emulation routines of several critical system instructions including LGDT and LIDT. The vulnerable code can be reached from unprivileged user code running inside hardware virtual machine (HVM) guests and can be used to escalate guest privileges. XSA 110 was reported by Jan Beulich from SUSE and concerns insufficient checks when emulating long jumps, calls or returns.

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