Category Archives: 0-day

December 2018 Patch Tuesday: Microsoft patches Windows zero-day exploited in the wild

It’s Patch Tuesday again and, as per usual, both Microsoft and Adobe have pushed out patches for widely-used software packages. The Microsoft patches Microsoft’s December 2018 Patch Tuesday release is pretty lightweight: the company has plugged 38 CVE-numbered security holes, nine of which are considered to be Critical. Among the most notable bugs in this batch are CVE-2018-8611, an elevation of privilege vulnerability that arises when the Windows kernel fails to properly handle objects in … More

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Adobe patches newly exploited Flash zero-day

Adobe has released an out-of-band security update for Flash Player that fixes two vulnerabilities, one of which is a zero-day (CVE-2018-15982) that has been spotted being exploited in the wild. About the vulnerability (CVE-2018-15982) CVE-2018-15982 is a use-after-free in the Flash’s file package com.adobe.tvsdk.mediacore.metadata that can be exploited to deliver and execute malicious code on a victim’s computer. It was flagged on November 29 by researchers with Gigamon Applied Threat Research (ATR) and Qihoo 360 … More

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Major flaws uncovered in leading IoT protocols

Trend Micro warned organizations to revisit their operational technology (OT) security after finding major design flaws and vulnerable implementations related to two popular machine-to-machine (M2M) protocols, Message Queuing Telemetry Transport (MQTT) and Constrained Application Protocol (CoAP). A high-level view of the interaction models of MQTT (left) and CoAP (right) The insecurity of IIoT’s data backbone Trend Micro’s new report, co-branded with Politecnico di Milano, The Fragility of Industrial IoT’s Data Backbone, highlights the growing threat … More

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Are we chasing the wrong zero days?

Zero days became part of mainstream security after the world found out that Stuxnet malware was used to inflict physical damage on an Iranian nuclear facility. After the revelation, organization focused efforts on closing unknown pathways into networks and to detecting unidentified cyber weapons and malware. A number of cybersecurity startups have even ridden the “zero day” wave into unicornville. Stuxnet’s ability to halt operations forced critical infrastructure operators to think about they could fall … More

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VirtualBox zero-day flaw released on Github; working exploit available but no patch

An independent researcher has turned a bit rogue, disclosing a zero-day vulnerability in the popular VirtualBox virtualization software while expressing deep disagreement with the state of security research, and bug bounty standards in particular.

In a meticulously crafted post on Github, Sergey Zelenyuk uses a default VirtualBox configuration to demonstrate a previously-unknown vulnerability that occurs due to memory corruption issues in Intel PRO / 1000 MT Desktop (82540EM) network cards (E1000) when the network mode is set to NAT (Network Address Translation).

“The E1000 has a vulnerability allowing an attacker with root/administrator privileges in a guest to escape to a host ring3. Then the attacker can use existing techniques to escalate privileges to ring 0 via /dev/vboxdrv,” Zelenyuk explains.

Ring 0 refers to the host machine, where the malicious program would essentially “escape” to execute arbitrary code. The exploit is replicable on Windows too, albeit with a few configuration exceptions. The flaw affects all current versions of VirtualBox (up to 5.2.20).

Zelenyuk not only wrote out a complete guide on how to replicate the attack, he even posted a demonstration video of him exploiting the flaw.

VirtualBox E1000 Guest-to-Host Escape from Sergey Zelenyuk on Vimeo.

In spite of the unethical nature of his disclosure, Zelenyuk is thoughtful enough to include a fix with his post.

“Until the patched VirtualBox build is out you can change the network card of your virtual machines to PCnet (either of two) or to Paravirtualized Network. If you can’t, change the mode from NAT to another one. The former way is more secure,” he writes.

As for his reasons for disclosing a zero-day publicly before Oracle gets a chance to patch the bug, the researcher expressed dissatisfaction with the infosec community – in particular, the rules enforced by contemporary bug bounty programs. While some may resonate with Zelenyuk’s arguments, publishing a zero-day openly for the whole Internet before the vendor can release a patch is nonetheless considered irresponsible disclosure. However, in cases where the vendor has been notified of the flaw months in advance and has failed to deliver (for one reason or another), such disclosures can get the ball rolling sooner rather than later. Hopefully Oracle delivers before bad actors exploit the bug, now that a working exploit is available. But the fact that there is now a window of opportunity for hackers is still an issue.

FireEye Uncovers CVE-2017-8759: Zero-Day Used in the Wild to Distribute FINSPY

FireEye recently detected a malicious Microsoft Office RTF document that leveraged CVE-2017-8759, a SOAP WSDL parser code injection vulnerability. This vulnerability allows a malicious actor to inject arbitrary code during the parsing of SOAP WSDL definition contents. FireEye analyzed a Microsoft Word document where attackers used the arbitrary code injection to download and execute a Visual Basic script that contained PowerShell commands.

FireEye shared the details of the vulnerability with Microsoft and has been coordinating public disclosure timed with the release of a patch to address the vulnerability and security guidance, which can be found here.

FireEye email, endpoint and network products detected the malicious documents.

Vulnerability Used to Target Russian Speakers

The malicious document, “Проект.doc” (MD5: fe5c4d6bb78e170abf5cf3741868ea4c), might have been used to target a Russian speaker. Upon successful exploitation of CVE-2017-8759, the document downloads multiple components (details follow), and eventually launches a FINSPY payload (MD5: a7b990d5f57b244dd17e9a937a41e7f5).

FINSPY malware, also reported as FinFisher or WingBird, is available for purchase as part of a “lawful intercept” capability. Based on this and previous use of FINSPY, we assess with moderate confidence that this malicious document was used by a nation-state to target a Russian-speaking entity for cyber espionage purposes. Additional detections by FireEye’s Dynamic Threat Intelligence system indicates that related activity, though potentially for a different client, might have occurred as early as July 2017.

CVE-2017-8759 WSDL Parser Code Injection

A code injection vulnerability exists in the WSDL parser module within the PrintClientProxy method ( - System.Runtime.Remoting/metadata/wsdlparser.cs,6111). The IsValidUrl does not perform correct validation if provided data that contains a CRLF sequence. This allows an attacker to inject and execute arbitrary code. A portion of the vulnerable code is shown in Figure 1.

Figure 1: Vulnerable WSDL Parser

When multiple address definitions are provided in a SOAP response, the code inserts the “//base.ConfigureProxy(this.GetType(),” string after the first address, commenting out the remaining addresses. However, if a CRLF sequence is in the additional addresses, the code following the CRLF will not be commented out. Figure 2 shows that due to lack validation of CRLF, a System.Diagnostics.Process.Start method call is injected. The generated code will be compiled by csc.exe of .NET framework, and loaded by the Office executables as a DLL.

Figure 2: SOAP definition VS Generated code

The In-the-Wild Attacks

The attacks that FireEye observed in the wild leveraged a Rich Text Format (RTF) document, similar to the CVE-2017-0199 documents we previously reported on. The malicious sampled contained an embedded SOAP monikers to facilitate exploitation (Figure 3).

Figure 3: SOAP Moniker

The payload retrieves the malicious SOAP WSDL definition from an attacker-controlled server. The WSDL parser, implemented in of .NET framework, parses the content and generates a .cs source code at the working directory. The csc.exe of .NET framework then compiles the generated source code into a library, namely http[url path].dll. Microsoft Office then loads the library, completing the exploitation stage.  Figure 4 shows an example library loaded as a result of exploitation.

Figure 4: DLL loaded

Upon successful exploitation, the injected code creates a new process and leverages mshta.exe to retrieve a HTA script named “word.db” from the same server. The HTA script removes the source code, compiled DLL and the PDB files from disk and then downloads and executes the FINSPY malware named “left.jpg,” which in spite of the .jpg extension and “image/jpeg” content-type, is actually an executable. Figure 5 shows the details of the PCAP of this malware transfer.

Figure 5: Live requests

The malware will be placed at %appdata%\Microsoft\Windows\OfficeUpdte-KB[ 6 random numbers ].exe. Figure 6 shows the process create chain under Process Monitor.

Figure 6: Process Created Chain

The Malware

The “left.jpg” (md5: a7b990d5f57b244dd17e9a937a41e7f5) is a variant of FINSPY. It leverages heavily obfuscated code that employs a built-in virtual machine – among other anti-analysis techniques – to make reversing more difficult. As likely another unique anti-analysis technique, it parses its own full path and searches for the string representation of its own MD5 hash. Many resources, such as analysis tools and sandboxes, rename files/samples to their MD5 hash in order to ensure unique filenames. This variant runs with a mutex of "WininetStartupMutex0".


CVE-2017-8759 is the second zero-day vulnerability used to distribute FINSPY uncovered by FireEye in 2017. These exposures demonstrate the significant resources available to “lawful intercept” companies and their customers. Furthermore, FINSPY has been sold to multiple clients, suggesting the vulnerability was being used against other targets.

It is possible that CVE-2017-8759 was being used by additional actors. While we have not found evidence of this, the zero day being used to distribute FINSPY in April 2017, CVE-2017-0199 was simultaneously being used by a financially motivated actor. If the actors behind FINSPY obtained this vulnerability from the same source used previously, it is possible that source sold it to additional actors.


Thank you to Dhanesh Kizhakkinan, Joseph Reyes, FireEye Labs Team, FireEye FLARE Team and FireEye iSIGHT Intelligence for their contributions to this blog. We also thank everyone from the Microsoft Security Response Center (MSRC) who worked with us on this issue.