Tag Archives: zeroday

Microsoft shuts down zero-day exploit on September Patch Tuesday

Microsoft shut down a zero-day vulnerability launched by a Twitter user in August and a denial-of-service flaw on September Patch Tuesday.

A security researcher identified by the Twitter handle SandboxEscaper shared a zero-day exploit in the Windows task scheduler on Aug. 27. Microsoft issued an advisory after SandboxEscaper uploaded proof-of-concept code on GitHub. The company fixed the ALPC elevation of privilege vulnerability (CVE-2018-8440) with its September Patch Tuesday security updates. A malicious actor could use the exploit to gain elevated privileges in unpatched Windows systems.

“[The attacker] can run arbitrary code in the context of local system, which pretty much means they own the box … that one’s a particularly nasty one,” said Chris Goettl, director of product management at Ivanti, based in South Jordan, Utah.

The vulnerability requires local access to a system, but the public availability of the code increased the risk. An attacker used the code to send targeted spam that, if successful, implemented a two-stage backdoor on a system.

“Once enough public information gets out, it may only be a very short period of time before an attack could be created,” Goettl said. “Get the Windows OS updates deployed as quickly as possible on this one.”

Microsoft addresses three more public disclosures

Administrators should prioritize patching three more public disclosures highlighted in September Patch Tuesday.

Microsoft resolved a denial-of-service vulnerability (CVE-2018-8409) with ASP.NET Core applications. An attacker could cause a denial of service with a specially crafted request to the application. Microsoft fixed the framework’s web request handling abilities, but developers also must build the update into the vulnerable application in .NET Core and ASP.NET Core.

Chris Goettl of IvantiChris Goettl

A remote code execution vulnerability (CVE-2018-8457) in the Microsoft Scripting Engine opens the door to a phishing attack, where an attacker uses a specially crafted image file to compromise a system and execute arbitrary code. A user could also trigger the attack if they open a specially constructed Office document.

“Phishing is not a true barrier; it’s more of a statistical challenge,” Goettl said. “If I get enough people targeted, somebody’s going to open it.”

This exploit is rated critical for Windows desktop systems using Internet Explorer 11 or Microsoft Edge. Organizations that practice least privilege principles can mitigate the impact of this exploit.

Another critical remote code execution vulnerability in Windows (CVE-2018-8475) allows an attacker to send a specially crafted image file to a user, who would trigger the exploit if they open the file.

September Patch Tuesday issues 17 critical updates

September Patch Tuesday addressed more than 60 vulnerabilities, 17 rated critical, with a larger number focused on browser and scripting engine vulnerabilities.

“Compared to last month, it’s a pretty mild month. The OS and browser updates are definitely in need of attention,” Goettl said.

Microsoft closed two critical remote code execution flaws (CVE-2018-0965 and CVE-2018-8439) in Hyper-V and corrected how the Microsoft hypervisor validates guest operating system user input. On an unpatched system, an attacker could run a specially crafted application on a guest operating system to force the Hyper-V host to execute arbitrary code.

Microsoft also released an advisory (ADV180022) for administrators to protect Windows systems from a denial-of-service vulnerability named “FragmentSmack” (CVE-2018-5391). An attacker can use this exploit to target the IP stack with eight-byte IP fragments and withholding the last fragment to trigger full CPU utilization and force systems to become unresponsive.

Microsoft also released an update to a Microsoft Exchange 2010 remote code execution vulnerability (CVE-2018-8154) first addressed on May Patch Tuesday. The fix corrects the faulty update that could break functionality with Outlook on the web or the Exchange Control Panel. 

“This might catch people by surprise if they are not looking closely at all the CVEs this month,” Goettl said.

Windows 10 zero-day disclosed on Twitter, no fix in sight

A mishandled disclosure process saw proof-of-concept code for a Windows 10 zero-day flaw released on Twitter, but Microsoft has no patch available.

A self-described retired vulnerability researcher who goes by the handle SandboxEscaper announced the Windows 10 zero-day on Twitter on Aug. 27, complete with proof-of-concept (POC) code hosted on GitHub, but didn’t notify Microsoft beforehand. The flaw is part of the Windows Task Scheduler, and it can allow an attacker to obtain system privileges.

According to the CERT Coordination Center (CERT/CC) advisory, the “Windows task scheduler contains a local privilege escalation vulnerability in the Advanced Local Procedure Call (ALPC) interface.”

“We have confirmed that the public exploit code works on 64-bit Windows 10 and Windows Server 2016 systems,” Will Dormann, vulnerability analyst for CERT/CC, wrote in the advisory. “Compatibility with other Windows versions may be possible with modification of the publicly-available exploit source code.”

Dormann also confirmed on Twitter that although the POC released by SandboxEscaper was designed to be a Windows 10 zero-day and affect 64-bit systems, the exploit would also work on 32-bit systems with “minor tweaks.”

Craig Young, computer security researcher at Tripwire, based in Portland, Ore., noted that the Windows 10 zero-day would allow “the caller to manipulate file permissions of protected system files.”

“This can be used to overwrite system libraries with malicious code to hijack Windows. With this published exploit code, it is trivial for malware to take complete control of the system after the malware has been loaded,” Young wrote via email. “Without a privilege escalation bug like this, the malware would be dependent on users clicking through access control alerts or entering administrator credentials.”

Risk vs. exploit code  

Experts generally agreed the level of risk for this Task Scheduler Windows 10 zero-day wouldn’t normally be too severe, because the exploit requires local access. This means an attacker would have to trick a user into downloading and running a malicious program, or they would need to have previously gained access to a system. However, experts said the release of the POC code changes the risk profile for the Windows 10 zero-day.

Allan Liska, solutions architect at Recorded Future, based in Somerville, Mass., added that this Windows 10 zero-day is another flaw in a long history of issues in the Windows Task Scheduler service.

“At this time, there is no patch for the vulnerability. One possible mitigation is to prevent untrusted — usually guest — users from running code. However, if an attacker gains access with user-level privilege, this mitigation will not work,” Liska said in an email. “The best bet until Microsoft releases a patch is to monitor for suspicious activity from Task Scheduler, and for this specific POC, monitor for the print spooler service spawning unusual processes,” he continued.

“Though bear in mind that while the POC uses the print spooler service, this vulnerability is not limited to just the print spooler. With some minor tweaking, the POC code could be used to execute other services.”

Although there were no specific details, SandboxEscaper expressed frustration with Microsoft and infosec in general before releasing the Windows 10 zero-day on Twitter, but appeared regretful two days later.

SandboxEscaper had mentioned a battle with depression and a desire to quit vulnerability research in a number of tweets leading up to releasing the POC code, and the vast majority of commenters offered messages of empathy or aid.

Microsoft did not respond to requests for comment at the time of this post.

August Patch Tuesday closes CPU bug, two zero-day exploits

Microsoft closed two zero-day vulnerabilities and released a fix for a new exploit for Intel processors on August Patch Tuesday.

Microsoft released an advisory (ADV-180018) on the latest speculative execution side channel vulnerability in Intel Core and Xeon processors called L1 Terminal Fault. Dubbed Foreshadow by security researchers, the vulnerability lets an attacker read data as it passes between a host and a virtual machine and a hypervisor.

The earlier Spectre and Meltdown variants allowed process-to-process interactions, but this latest hardware exploit allows a guest system to retrieve data from another guest system, said Brian Secrist, content manager at Ivanti, based in South Jordan, Utah.  

Once again, we have a bunch of hoops to jump through to get to full remediation… 2018 is keeping us real busy.
Brian Secristcontent manager, Ivanti

Full protection from Foreshadow (CVE-2018-3615, CVE-2018-3620 and CVE-2018-3646) on Windows requires a registry change, Microsoft patch and Intel firmware update to close the vulnerability.

“Once again, we have a bunch of hoops to jump through to get to full remediation,” Secrist said. “2018 is keeping us real busy.”

Microsoft addresses two zero-day exploits

Microsoft also closed a pair of zero-day remote code execution vulnerabilities. The first (CVE-2018-8373), in the Microsoft Scripting Engine with known exploits that affect all versions of Internet Explorer, allows an attacker to run arbitrary code on unpatched machines in the context of users who visit a specially crafted website. Depending on the user’s rights, the attacker could install programs or view and delete data. The patch changes how the scripting engine handles objects in memory. This CVE is critical for Windows desktop systems and important for server versions.

Rated important, the second zero-day (CVE-2018-8414) uses a Windows Shell bug in Windows 10 and Windows Server SAC Server Core for remote-code execution attacks. This vulnerability requires the user to run a malicious file either from email or a web site, after which an attacker can run code at the privilege level of the current user. The patch makes Windows Shell validate file paths properly.

August Patch Tuesday closes more than 60 vulnerabilities

More than half of the 60 vulnerabilities disclosed in August Patch Tuesday affect browsers or the scripting engine. Administrators should prioritize patching workstations and servers for a critical remote code execution vulnerability (CVE-2018-8345) that triggers when viewed by a user. Microsoft resolved this exploit by correcting the processing of shortcut .LNK references.

“Because the user doesn’t have to click on the malicious .LNK file to actually exploit the vulnerability, compared to browser vulnerability, it’s more likely for a server admin to be browsing through files. If they see this shortcut and the system renders it, then that’s when the exploit runs,” said Jimmy Graham, director of product management at Qualys, based in Foster City, Calif.

Jimmy Graham, QualysJimmy Graham, Qualys

Almost every major third-party vendor released patches and updates between the July and August Patch Tuesday, said Secrist. Adobe released four updates, including fixes for Adobe Flash and Acrobat. Google Chrome released version 68, and Firefox released updates for Thunderbird.

“We haven’t seen any increase in attacks or anything, just an example of better research and better coverage of vulnerabilities,” Secrist said.

July Patch Tuesday issues anger IT workers

After the July Patch Tuesday releases, Microsoft warned customers of potential SQL Server startup problems on Windows desktop (7 and 8.1) and server (2008 R2 and 2012 R2) versions on July 26. The company released several hotfixes and recommended uninstalling the July patches. Such rollbacks of faulty Microsoft updates have become a recurring headache for administrators.

Microsoft security updates for July also caused problems for the .NET Framework. On July 16, Microsoft posted a blog that “encouraged” Exchange customers to delay applying the July 10 updates to avoid disruptions with mail delivery. Hotfixes for affected systems — all supported versions of Windows Server — did not arrive until July 17. Up until that point, the only remedy was to uninstall the .NET Framework 4.7.2 update.

“Clearly there is a quality assurance issue of some kind,” Secrist said. “There’s another .NET release this month. Hopefully they spend more time on this one. We always strongly recommend you run [patches] through a test group and make sure they are stable before you push them out.”

Jeff Guillet, CEO of EXPTA Consulting in Pacifica, Calif., reached out to the Exchange product group for more information when the disruptions first occurred and said it was a two-fold problem of “really bad patches and bad communication.”

“Nobody even acknowledged that there was a problem and then all of a sudden they said, ‘Oh, by the way, we fixed this.’ [Administrators] had to troubleshoot it themselves because there was no communication from Microsoft saying this was a problem,” said Guillet.

While the intent of Patch Tuesday is to protect systems from vulnerabilities, the recent spate of patching issues concerns some IT administrators.

“Everybody’s kind of come to terms with [monthly patching], but the expectation was that a patch isn’t going to break stuff,” said Guillet. “So if it’s going to start breaking things, now I need to worry about testing it and I don’t have time because the next patches are coming up next Tuesday.”

Adobe zero-day fix precedes June Patch Tuesday

An Adobe zero-day vulnerability in Flash Player that was actively exploited stirred up excitement for admins in the week leading up to June Patch Tuesday.

Adobe released a fix for the zero-day (CVE-2018-5002) and three other vulnerabilities for the Windows client operating system on June 7.

The zero-day exploit launched its attacks from Excel documents sent via email. Users who open these infected Excel attachments on unpatched systems could allow the execution of arbitrary code under the exploited user account.

Chris Goettl, director of product management, IvantiChris Goettl

After the Adobe zero-day issue, the patching workload for administrators is lighter than usual for June Patch Tuesday, with about 50 unique vulnerabilities to correct — including 11 rated critical.

“Our recommendation is the Flash patch — if it already hasn’t been pushed out, [give that] high priority,” said Chris Goettl, director of product management at Ivanti, based in South Jordan, Utah.

June Patch Tuesday closes about 50 vulnerabilities

Microsoft released an update for the only publicly disclosed vulnerability (CVE-2018-8267) for June Patch Tuesday, which affects the Microsoft scripting engine on all supported versions of Internet Explorer. Attacks can exploit this flaw through a compromised website, or user-contributed ads or content, to take control of the target machine.

On an unpatched system, attackers could execute arbitrary code as the hacked user. Organizations that follow least-privilege rules that restrict the use of higher full permissions will reduce the damage from a breach.

Jimmy Graham, director of product management at QualysJimmy Graham

Microsoft’s June Patch Tuesday fixes also closed a remote code execution vulnerability (CVE-2018-8225) that affects all supported versions of Windows. This vulnerability could allow an attacker to compromise systems through a domain name system (DNS) server.

“That would be higher risk for mobile workstations, where it’s likely the system will be accessing an untrusted DNS server through public Wi-Fi,” said Jimmy Graham, director of product management at Qualys, based in Redwood City, Calif.

A memory corruption vulnerability (CVE-2018-8229) in the Edge browser’s Chakra scripting engine would let an attacker exploit an unpatched system through specially crafted websites or user-provided content. The effects depend on the level of privilege on the system.

Spectre vulnerabilities continue

Just when it seemed the Meltdown and Spectre vulnerabilities were winding down, security researchers uncovered another CPU bug. The vulnerability, called Spectre variant 4, is similar to the other speculative execution side-channel vulnerabilities disclosed in January, but they are rated with moderate severity.  

Jann Horn, a security researcher at Google’s Project Zero, and Ken Johnson, of the Microsoft Security Response Center, discovered Spectre variant 4 (CVE-2018-3639). This exploit enables malicious actors to read privileged data across trust boundaries.

Microsoft released its ADV180012 advisory in January to assist administrators with closing the exploits from the speculative execution side-channel vulnerabilities. The company continues to update the site, and it added further mitigation instructions to address Spectre variant 4. There are still no active attacks on Meltdown or Spectre, but administrators should install the patches and microcode updates when the CPU manufacturers release them.

For more information about the remaining security bulletins for June Patch Tuesday, visit Microsoft’s Security Update Guide.

IOHIDeous is a macOS zero-day for the New Year

In a somewhat unorthodox New Year’s gift, a developer detailed a long-unpatched macOS zero-day flaw that could allow an attacker root access for full system compromise, although it cannot be exploited remotely.

Siguza, a hobbyist developer and hacker from Switzerland, described in great detail a zero-day vulnerability, dubbed IOHIDeous, which is said to affect all versions of macOS going back 15 years.

“This is the tale of a macOS-only vulnerability in IOHIDFamily that yields kernel [read and write] and can be exploited by any unprivileged user,” Siguza wrote in a Github post. “IOHIDFamily has been notorious in the past for the many race conditions it contained, which ultimately lead to large parts of it being rewritten to make use of command gates, as well as large parts being locked down by means of entitlements. I was originally looking through its source in the hope of finding a low-hanging fruit that would let me compromise an iOS kernel, but what I didn’t know it then [sic] is that some parts of IOHIDFamily exist only on macOS – specifically IOHIDSystem, which contains the vulnerability discussed herein.”

Siguza released proof-of-concept (PoC) exploit code for IOHIDeous but noted that not all of the parts have been tested across all versions of macOS. Part of the attack used “doesn’t work on High Sierra 10.13.2 anymore,” but Siguza said the vulnerability is still present and may be exploitable in different ways. Siguza successfully tested other portions of the PoC attack on High Sierra and assumed to work on other versions of macOS or stated to be easily adapted for other versions.

However, while exploiting the IOHIDeous macOS zero-day could allow for an attacker to escalate privilege, run arbitrary code and gain root access, Siguza said on Twitter that the risks are somewhat lessened because the flaw is not remotely exploitable and because “triggering [the] bug is pretty noticeable with the entire UI being torn down and whatnot…”

Siguza also commented on why IOHIDeous details were released publicly and not sold either on the dark web or to a bug bounty program.

“My primary goal was to get the write-up out for people to read. I wouldn’t sell to blackhats because I don’t wanna help their cause. I would’ve submitted to Apple if their bug bounty included macOS, or if the vuln was remotely exploitable,” Siguza wrote on Twitter. “Since neither of those were the case, I figured I’d just end 2017 with a bang because why not. But if I wanted to watch the world burn, I would be writing zero-day ransomware rather than write-ups ;)”

As of the time of this post, Apple has not responded to requests for comment or released information about any potential IOHIDeous patch.