Warning — Two Unpatched Critical 0-Day RCE Flaws Affect All Windows Versions

Mar 23, 2020

Microsoft today issued a new security advisory warning
billions of Windows users of two new critical, unpatched zero-day
vulnerabilities that could let hackers remotely take complete
control over targeted computers.

According to Microsoft ^[1], both unpatched flaws
are being used in limited, targeted attacks and impact all
supported versions of the Windows operating system—including
Windows 10, 8.1 and Server 2008, 2012, 2016, and 2019 editions, as
well as Windows 7 for which Microsoft ended its support on
January 14, 2020.

Both vulnerabilities reside in the Windows Adobe Type Manager
Library, a font parsing software that not only parses content
when open with a 3rd-party software but also used by Windows
Explorer to display the content of a file in the ‘Preview Pane’ or
‘Details Pane’ without having users to open it.

The flaws exist in Microsoft Windows when the Adobe Type Manager
Library improperly “handles a specially-crafted multi-master font –
Adobe Type 1 PostScript format,” allowing remote attackers to
execute arbitrary malicious code on targeted systems by convincing
a user to open a specially crafted document or viewing it in the
Windows Preview pane.

“For systems running supported versions of Windows 10, a successful
attack could only result in code execution within an AppContainer
sandbox context with limited privileges and capabilities,”
Microsoft said.

At this moment, though it’s not clear if the flaws can also be
triggered remotely over a web browser by convincing a user to visit
a web-page containing specially-crafted malicious OTF fonts, there
are multiple other ways an attacker could exploit the
vulnerability, such as through the Web Distributed Authoring and
Versioning (WebDAV) client service.

No Patch Yet Available; Apply Workarounds

Microsoft said it’s aware of the issue and working on a patch,
which the company would release to all Windows users as part of its
next Patch Tuesday updates, on 14th April.

“Enhanced Security Configuration does not mitigate this
vulnerability,” the company added.

1) Disable the Preview Pane and Details Pane in Windows
Explorer

Meanwhile, all Windows users are highly recommended to disable the
Preview Pane and Details Pane feature in Windows Explorer as a
workaround to
reduce the risk ^[2]
of getting hacked by opportunistic attacks.
To disable the Preview Pane and Details Pane feature:

Open Windows Explorer, click Organize and then click
Layout.
Clear both the Details pane and Preview pane menu options.
Click Organize, and then click Folder and search options.
Click the View tab.
Under Advanced settings, check the Always show icons, never
thumbnails box.
Close all open instances of Windows Explorer for the change to
take effect.

However, to be noted, while this workaround prevents malicious
files from being viewed in Windows Explorer, it does not strict any
legitimate 3rd-party software from loading the vulnerable font
parsing library.

2) Disable the WebClient service

Besides this, it is also advised to disable Windows WebClient
service to prevent cyberattacks through the WebDAV client service.

Click Start, click Run (or press the Windows Key and R on the
keyboard), type Services.msc and then click OK.
Right-click WebClient service and select Properties.
Change the Startup type to Disabled. If the service is running,
click Stop.
Click OK and exit the management application.

“After applying this workaround, it is still possible for remote
attackers who successfully exploit this vulnerability to cause the
system to run programs located on the targeted user’s computer or
the Local Area Network (LAN), but users will be prompted for
confirmation before opening arbitrary programs from the Internet,”
the Microsoft warned.

3) Rename or Disable ATMFD.DLL

Microsoft is also urging users to rename Adobe Type Manager Font
Driver (ATMFD.dll) file to temporarily disable the embedded font
technology, which could cause certain 3rd-party apps to stop
working.

Enter the following commands at an administrative command
prompt:

For 32-bit system:
cd “%windir%\system32”
takeown.exe /f atmfd.dll
icacls.exe atmfd.dll /save atmfd.dll.acl
icacls.exe atmfd.dll /grant Administrators:(F)
rename atmfd.dll x-atmfd.dll

For 64-bit system:
cd “%windir%\system32”
takeown.exe /f atmfd.dll
icacls.exe atmfd.dll /save atmfd.dll.acl
icacls.exe atmfd.dll /grant Administrators:(F)
rename atmfd.dll x-atmfd.dll
cd “%windir%\syswow64”
takeown.exe /f atmfd.dll
icacls.exe atmfd.dll /save atmfd.dll.acl
icacls.exe atmfd.dll /grant Administrators:(F)
rename atmfd.dll x-atmfd.dll

Restart the system.

References

^{^}
Microsoft
(portal.msrc.microsoft.com)
^{^}
workaround to reduce the risk
(portal.msrc.microsoft.com)

The Hacker News Headlines

New Apple iOS 16 Exploit Enables Stealthy Cellular Access Under Fake Airplane Mode

Aug 18, 2023

The Hacker News Headlines

China-Linked Bronze Starlight Group Targeting Gambling Sector with Cobalt Strike Beacons

Aug 18, 2023

The Hacker News Headlines

NoFilter Attack: Sneaky Privilege Escalation Method Bypasses Windows Security

Aug 18, 2023

OWASP TOP !0

Injection. Injection flaws, such as SQL, NoSQL, OS, and LDAP injection, occur when untrusted data is sent to an interpreter as part of a command or query. The attacker’s hostile data can trick the interpreter into executing unintended commands or accessing data without proper authorization. Broken Authentication. Application functions related to authentication and session management are often implemented incorrectly, allowing attackers to compromise passwords, keys, or session tokens, or to exploit other implementation flaws to assume other users’ identities temporarily or permanently. Sensitive Data Exposure. Many web applications and APIs do not properly protect sensitive data, such as financial, healthcare, and PII. Attackers may steal or modify such weakly protected data to conduct credit card fraud, identity theft, or other crimes. Sensitive data may be compromised without extra protection, such as encryption at rest or in transit, and requires special precautions when exchanged with the browser. XML External Entities (XXE). Many older or poorly configured XML processors evaluate external entity references within XML documents. External entities can be used to disclose internal files using the file URI handler, internal file shares, internal port scanning, remote code execution, and denial of service attacks. Broken Access Control. Restrictions on what authenticated users are allowed to do are often not properly enforced. Attackers can exploit these flaws to access unauthorized functionality and/or data, such as access other users’ accounts, view sensitive files, modify other users’ data, change access rights, etc. Security Misconfiguration. Security misconfiguration is the most commonly seen issue. This is commonly a result of insecure default configurations, incomplete or ad hoc configurations, open cloud storage, misconfigured HTTP headers, and verbose error messages containing sensitive information. Not only must all operating systems, frameworks, libraries, and applications be securely configured, but they must be patched/upgraded in a timely fashion. Cross-Site Scripting XSS. XSS flaws occur whenever an application includes untrusted data in a new web page without proper validation or escaping, or updates an existing web page with user-supplied data using a browser API that can create HTML or JavaScript. XSS allows attackers to execute scripts in the victim’s browser which can hijack user sessions, deface web sites, or redirect the user to malicious sites. Insecure Deserialization. Insecure deserialization often leads to remote code execution. Even if deserialization flaws do not result in remote code execution, they can be used to perform attacks, including replay attacks, injection attacks, and privilege escalation attacks. Using Components with Known Vulnerabilities. Components, such as libraries, frameworks, and other software modules, run with the same privileges as the application. If a vulnerable component is exploited, such an attack can facilitate serious data loss or server takeover. Applications and APIs using components with known vulnerabilities may undermine application defenses and enable various attacks and impacts. Insufficient Logging & Monitoring. Insufficient logging and monitoring, coupled with missing or ineffective integration with incident response, allows attackers to further attack systems, maintain persistence, pivot to more systems, and tamper, extract, or destroy data. Most breach studies show time to detect a breach is over 200 days, typically detected by external parties rather than internal processes or monitoring.

Warning — Two Unpatched Critical 0-Day RCE Flaws Affect All Windows Versions