ERNW White Paper 70 – HL7 FHIR: Preserving Distributed Resource Integrity

With this blog post I am pleased to announce the publication of a new ERNW White Paper about the HL7 FHIR communication standard.


Digital networking is already widespread in many areas of life. More and more medical devices are also being networked in the healthcare industry. This growth makes the development and use of new medical communication standards necessary since existing solutions can only meet the changing requirements with great effort. The HL7 FHIR standard is an example of such a medical communication standard. FHIR is said to have increased the interoperability between different medical contexts,e.g., administration, billing, and clinical care, to enable data exchange of various systems. The FHIR standard addresses the security risks associated with strongly networked communication from a large number of systems across the trust and organizational boundaries only indirectly because FHIR does not define mandatory security controls or requirements.

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Breaking, Misc

Root Cause Analysis of a Heap-Based Buffer Overflow in GNU Readline

In the last blog post, we discussed how fuzzers determine the uniqueness of a crash. In this blog post, we discuss how we can manually triage a crash and determine the root cause. As an example, we use a heap-based buffer overflow I found in GNU readline 8.1 rc2, which has been fixed in the newest release. We use GDB and rr for time-travel debugging to determine the root cause of the bug.

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Security Advisories for SolarWinds N-Central

In August 2020 we reported six vulnerabilities in SolarWinds N-Central to the vendor.
The following CVE IDs were assigned to the issues :
  • CVE-2020-25617: RCE in N-Central Administration Console (AdvancedScripts Endpoint)
  • CVE-2020-25618: Local Privilege Escalation from nable User to root (N-Central Backend Server)
  • CVE-2020-25619: Access to Internal Services through SSH Port Forwarding (N-Central Backend Server)
  • CVE-2020-25620: SolarWinds Support Account with Default Credentials
  • CVE-2020-25621: Local Database does not require Authentication (N-Central Backend Server)
  • CVE-2020-25622: CSRF in N-Central Administration Console (AdvancedScripts Endpoint)
The vulnerabilities have been found in the course of an extensive research project, in which we analyze the security of multiple Unified Endpoint Management (UEM) solutions. Similar vulnerabilities have been found in other solutions as we pointed out in previous posts about the Ivanti DSM Suite and Nagios XI. The final outcome of the research project will be published as a whitepaper and possibly conference talk as soon as the project including all disclosure processes concludes.
We will provide a short description of the CVEs outlining the impact of the vulnerabilities. Technical details will be published in a whitepaper as mentioned above. All six vulnerabilities have been verified for SolarWinds N-Central
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VMware NSX-T MITM Vulnerability (CVE-2020-3993)

NSX-T is a Software-Defined-Networking (SDN) solution of VMware which, as its basic functionality, supports spanning logical networks across VMs on distributed ESXi and KVM hypervisors. The central controller of the SDN is the NSX-T Manager Cluster which is responsible for deploying the network configurations to the hypervisor hosts.

This summer, I looked into the mechanism which is used to add new KVM hypervisor nodes to the SDN via the NSX-T Manager. By tracing what happens on the KVM host, I discovered that the KVM hypervisor got instructed to download the NSX-T software packages from the NSX-T Manager via unencrypted HTTP and install them without any verification. This enables a Man-in-the-Middle (MITM) attacker on the network path to replace the downloaded packages with malicious ones and compromise the KVM hosts.

After disclosing this issue to VMware, they developed fixes and published the vulnerability in VMSA-2020-0023 assigning a CVSSv3 base score of 7.5.

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XSS Vulnerability in Froala WYSIWYG HTML Editor

Recently, I had a brief look at the Froala WYSIWYG HTML Editor (v3.2.0) as there was a post about it on the Full Disclosure mailing list.

When targeting a HTML Editor, I guess one of the first things that everybody does is to check for XSS vulnerabilities. So I tried the usual XSS payloads (a great resource for XSS payloads is the XSS cheat sheet by PortSwigger) within the editor’s code view, but did not have much luck with the common payloads as they were filtered. However, using the HTML object tag, it was possible to trigger an XSS.

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Microsoft Office Telemetry: Report Release

The German Federal Office for Information Security (orig., ger., Bundesamt für Sicherheit in der Informationstechnik – BSI) has published our report on Microsoft Office Telemetry.

Microsoft has released a set of privacy settings for Office, one of which enables users to configure the type and amount of diagnostic (i.e., telemetry) data that Office may send to Microsoft. When deployed, it is available in the form of a group policy setting. It allows users to configure one of the following diagnostic data levels: required, optional, or neither.  The report we produced:

  • analyzes the impact of the required, optional, and neither diagnostic data levels on the output of diagnostic data produced by Office; and
  • provides and evaluates approaches for partially or fully disabling the output of diagnostic data produced by Office.

The report is available here (in English).

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Forklift <=3.3.9 and <=3.4 Local Privilege Escalations on macOS (CVE-2020-15349/CVE-2020-27192)

I have started to have a look at my local installed helpers on macOS. These helpers are used as an interface for applications to perform privileged operations on the system. Thus, it is quite a nice attack surface to search for Local Privilege Escalations.

Forklift is an advanced dual pane file manager for macOS. It is well known under macOS power users.

As part of my investigation I identified vulnerabilities in Forklift allowing local privilege escalation.

By now all vulnerabilities are fixed by the vendor I can release the details:

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Reversing C++ Without Getting a Heart Attack – DEvirtualize VIrtual Calls With Devi

TLDR: This blogpost presents devi, a tool that can help you devirtualize virtual calls in C++ binaries. It uses Frida to trace the execution of a binary and uncover the call sources and destinations of virtual calls. The collected information can then be viewed in IDA Pro, Binary Ninja, or Ghidra. The plugin adds the respective control-flow edges allowing further analysis (using different plugins) or simply providing more comfort when analyzing C++ binaries.

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