Miscreants fling booby-trapped Office files at victims, no patch yet, says Microsoft
- Reference: 1631053225
- News link: https://www.theregister.co.uk/2021/09/07/microsoft_office_zero_day/
- Source link:
The vulnerability, CVE-2021-40444, [1]is described as a hole in MSHTML, Internet Explorer's browser engine. Miscreants are seemingly placing a malicious ActiveX control in an Office document and convincing victims to open or view it, potentially achieving remote code execution.
"Microsoft is investigating reports of a remote code execution vulnerability in MSHTML that affects Microsoft Windows," the IT giant stated.
[2]
"Microsoft is aware of targeted attacks that attempt to exploit this vulnerability by using specially-crafted Microsoft Office documents."
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It went on to say how others could also exploit the bug, for which no patch exists yet: "An attacker could craft a malicious ActiveX control to be used by a Microsoft Office document that hosts the browser rendering engine. The attacker would then have to convince the user to open the malicious document. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights."
The vulnerability was reported to Redmond on Sunday by the team at malware detection biz, EXPMON, who were credited with the discovery along with a Microsoft staffer and three researchers at security shop Mandiant. US CERT has also [5]issued a warning for IT admins to protect their systems.
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"We have reproduced the attack on the latest Office 2019/Office 365 on Windows 10 (typical user environment), for all affected versions please read the Microsoft Security Advisory," [7]EXPMON said . "The exploit uses logical flaws so the exploitation is perfectly reliable (& dangerous)."
[8]Microsoft, Google, Citizen Lab blow lid off zero-day bug-exploiting spyware sold to governments
[9]Microsoft faces up to an old foe with out-of-band patch for PDF weirdness
[10]South Korea kills ActiveX-based government digital certificate service
[11]US-CERT lists the 10 most-exploited security bugs and, yeah, it's mostly Microsoft holes people forgot to patch
Well, up to a point. Microsoft noted that there are mitigations already in place:
By default, Microsoft Office opens documents from the internet in Protected View or Application Guard for Office both of which prevent the current attack.
And its antivirus tools should be able to detect the exploit:
Microsoft Defender Antivirus and Microsoft Defender for Endpoint both provide detection and protections for the known vulnerability. Customers should keep antimalware products up to date. Customers who utilize automatic updates do not need to take additional action. Enterprise customers who manage updates should select the detection build 1.349.22.0 or newer and deploy it across their environments. Microsoft Defender for Endpoint alerts will be displayed as: “Suspicious Cpl File Execution”.
Microsoft is no doubt working on a fix – perhaps in time for next week's Patch Tuesday – though as a workaround for now, you can protect yourself further by disabling the installation of all ActiveX controls by altering the registry and rebooting. There are [12]full details here. ®
Get our [13]Tech Resources
[1] https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-40444
[2] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_security/front&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=2&c=2YTg1fHwwlKkJBIhczPbyuQAAAFE&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0
[3] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_security/front&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44YTg1fHwwlKkJBIhczPbyuQAAAFE&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[4] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_security/front&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=3&c=33YTg1fHwwlKkJBIhczPbyuQAAAFE&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dmid%26test%3D0
[5] https://twitter.com/USCERT_gov/status/1435342618704191491
[6] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_security/front&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44YTg1fHwwlKkJBIhczPbyuQAAAFE&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[7] https://twitter.com/EXPMON_/status/1435310341689331721
[8] https://www.theregister.com/2021/07/16/microsoft_candiru_malware/
[9] https://www.theregister.com/2021/06/30/microsoft_internet_explorer_pdf_patch/
[10] https://www.theregister.com/2020/12/10/south_korea_activex_certs_dead/
[11] https://www.theregister.com/2020/05/14/uscert_most_pwned_bugs/
[12] https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-40444
[13] https://whitepapers.theregister.com/
Microsoft actively try to prevent users running as admin with UAC. It is the many crappy 3rd party apps that try to write places they shouldn't that lead people to run as administrator. Even then, it isn't usually required. You just need to identify which bits of the filesystem and registry they are trying to write to and adjust permissions as required. However, the vendor will just tell you to run as admin.
An unfortunate side effect of UAC are applications like Chrome or Slack that by default download and run from user profiles. Microsoft are guilty of this as well with things like Teams. There are machine wide installers for most of these if you take the effort to find them. We normally just block executables from running from profiles.
I do not think Microsoft is off the hook when it comes to needing admin privileges for many everyday things in Windows. Just look at printing, especially after the latest printnightmare patch.
It think it is because there is too much stuff in Windows that has to be tweaked 'on the fly' to get work done. So Windows is set up not to treat 'admin' as a separate user (where you'd have to close your work, log off and then log on as admin) but an attribute you can attach to a normal user. Just to nudge the OS along as a normal part of your work flow.
*NIXes encourage you to think things through and get everything properly configured as a separate process.
"Windows is set up not to treat 'admin' as a separate user"
Wrong. It was designed like this from day one (NT was anyway, forget about Windows 95/98/ME).
The problem was people didn't want to run as a non admin user because they didn't want to have to log off and back on to change settings, so just ended up running as an admin user all the time. This led MS to implement UAC.
Microsoft could have easily alleviated this by providing an easy admin role tool, some equivalent of sudo or su. runas did not exist back then.
unbelievable!
You would have thought that, by now, the number of "holes" in Microsoft Office would be nil. Do they ever review and test their code? You get the impression that the, already bloated, code is just patch and tweaked to add features (that nobody asked for) and there is lots redundant code and API calls just left in place.
Re: unbelievable!
It is a structural issue. The most important person in any Microsoft team is the program manager. Their goal is to push through features. If you used any of their API’s you would realize that it be is very easy to crash office. They measure their success based on their ability to push through their particular feature.
They are better than before but office is its own beast.
ActiveX still around?
Shouldn’t the presence of activex be the reason for search engines to red flag these sites?
"Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights."
Why has Microsoft made it so easy (and sometimes necessary) to run as an administrator rather than as a user with limited permissions? This makes every exploit potentially more dangerous.