Microsoft Issues Emergency Patch For Under-Attack IE Zero Day

Dec 20, 2018

Microsoft today issued an out-of-band security update to patch
a critical zero-day vulnerability in Internet Explorer (IE) Web
browser that attackers are already exploiting in the wild to hack
into Windows computers.

Discovered by security researcher Clement Lecigne of Google’s
Threat Analysis Group, the vulnerability, tracked as CVE-2018-8653,
is a remote code execution (RCE) flaw in the IE browser’s scripting
engine.

According to the advisory, an unspecified memory corruption
vulnerability resides in the scripting engine JScript component of
Microsoft Internet Explorer that handles execution of scripting
languages.

If exploited successfully, the vulnerability could allow attackers
to execute arbitrary code in the context of the current user.

“If the current user is logged on with administrative user rights,
an attacker who successfully exploited the vulnerability could take
control of an affected system. An attacker could then install
programs; view, change, or delete data; or create new accounts with
full user rights,” the advisory ^[1] reads.

Besides this, a remote attacker can also target victims by
convincing them into viewing a specially crafted HTML document
(e.g., a web page or an email attachment), MS Office document, PDF
file or any other document that supports embedded IE scripting
engine content.

The IE zero-day vulnerability impacts IE 9 on Windows Server
2008, IE 10 on Windows Server 2012, IE 11 from Windows 7 to Windows
10, and IE 11 on Windows Server 2019, Windows Server 2016, Windows
Server 2008 R2, Windows Server 2012 R2.

Neither Google nor Microsoft has yet publicly disclosed any
technical details about the IE zero-day vulnerability,
proof-of-concept exploit code, or details about the ongoing cyber
attack campaign utilizing this RCE bug.

Since the vulnerability is actively being exploited in the wild
which makes it a critical zero-day flaw, users are strongly
recommended to install the latest updates provided by Microsoft as
soon as possible.

Though it is not recommended, users who cannot immediately deploy
patches can mitigate the threat by restricting access to
jscript.dll file by running following command in the command prompt
using admin privileges.

For 32-bit System — cacls %windir%\system32\jscript.dll /E /P
everyone:N

For 64-bit System — cacls %windir%\syswow64\jscript.dll /E /P
everyone:N

It should be noted that the above command will force the web
browser to use Jscript9.dll, but any website that relies on
Jscript.dll will fail to render.

References

^{^}
advisory
(portal.msrc.microsoft.com)

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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.

Microsoft Issues Emergency Patch For Under-Attack IE Zero Day

References

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