CVE-2016-3298
Microsoft Internet Explorer Messaging API Information Disclosure Vulnerability
Description
CVE-2016-3298 is an information disclosure vulnerability in the Microsoft Internet Messaging API that allows an attacker to test for the presence of files on disk. The vulnerability occurs because the API improperly handles objects in memory, creating an information leak that can be exploited through a crafted web page. An attacker who successfully exploits CVE-2016-3298 can determine whether specific files exist on the target system, enabling reconnaissance for follow-up attacks. CISA has added this vulnerability to its KEV catalog, and the EPSS percentile of 96.4% indicates very high exploitation activity.
KEV Information
CVSS Score
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:NOpen in CalculatorAffected Products
| Vendor | Product | Version |
|---|---|---|
| microsoft | internet explorer | 9; 10; 11 |
| microsoft | windows 7 | - |
| microsoft | windows server 2008 | -; r2 |
| microsoft | windows vista | - |
Multiple CVSS Assessments
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
References
- http://www.securityfocus.com/bid/93392(Broken Link, Third Party Advisory, VDB Entry)
- http://www.securitytracker.com/id/1036992(Broken Link, Third Party Advisory, VDB Entry)
- https://docs.microsoft.com/en-us/security-updates/securitybulletins/2016/ms16-118(Patch, Vendor Advisory)
- https://docs.microsoft.com/en-us/security-updates/securitybulletins/2016/ms16-126(Patch, Vendor Advisory)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2016-3298(US Government Resource)
Weakness Type
CWE-200: Exposure of Sensitive Information to an Unauthorized Actor
CWE-200 describes a weakness where a product exposes sensitive information to unauthorized actors. In CVE-2016-3298, the Microsoft Internet Messaging API improperly handles objects in memory, allowing remote attackers to determine whether specific files exist on the victim's local file system through crafted web content served via Internet Explorer.
Learn more: CWE-200 — Exposure of Sensitive Information to an Unauthorized Actor
Impact Analysis
CVE-2016-3298 primarily impacts confidentiality by enabling remote file existence detection on target systems. The vulnerability is exploitable through the network via a crafted web page viewed in Internet Explorer, requiring user interaction but no authentication. While the direct impact is limited to information disclosure, this reconnaissance capability is commonly used in exploit kit operations to fingerprint target systems and identify installed security products before delivering exploit payloads. The EPSS percentile of 96.4% reflects very high exploitation activity, confirming widespread use in attack campaigns. CISA has confirmed active exploitation and added CVE-2016-3298 to the KEV catalog.
Exploit Maturity
CISA has confirmed active exploitation of CVE-2016-3298 in the wild and added it to the Known Exploited Vulnerabilities catalog with a remediation deadline of June 14, 2022. The EPSS percentile of 96.4% indicates very high exploitation probability. This type of file detection vulnerability is a standard component in exploit kit operations, where it serves as a reconnaissance tool to profile target systems and decide whether to deliver secondary payloads. The vulnerability was actively used in exploit kit campaigns to detect the presence of security analysis tools, antivirus software, and virtual machine indicators on potential victim systems.
Remediation
- Apply Microsoft security updates as directed by the vendor. This is the required remediation action per CISA's KEV catalog entry for CVE-2016-3298.
- Migrate away from Internet Explorer to a modern browser such as Microsoft Edge, Google Chrome, or Mozilla Firefox, as Internet Explorer has reached end of life.
- Implement browser hardening measures, including restricting ActiveX controls and limiting script execution from untrusted sources through Internet Explorer security settings and Group Policy.
- Deploy web content filtering solutions to block access to known exploit kit domains and detect exploitation attempts targeting the Internet Messaging API.
- Monitor endpoint logs for indicators of browser-based reconnaissance, including unusual API calls related to the Internet Messaging API and file system probing activity.
Technical Details
CVE-2016-3298 resides in the Microsoft Internet Messaging API, a component accessible through Internet Explorer. The vulnerability is triggered when the API improperly handles objects in memory during certain operations, classified under CWE-200 (Exposure of Sensitive Information). By crafting specific requests through the Internet Messaging API from a web page, an attacker can observe differences in the API's behavior when referencing existing versus non-existing files, effectively creating a file existence oracle. The attack vector is network-based, requiring the victim to visit a malicious web page in Internet Explorer, but no authentication is needed. This vulnerability is functionally similar to other Internet Explorer information disclosure flaws (such as CVE-2016-0162 and CVE-2016-3351) that were contemporaneously used in exploit kit campaigns for target fingerprinting.
Frequently Asked Questions
Is CVE-2016-3298 being actively exploited?
Yes, CVE-2016-3298 has been actively exploited in the wild. CISA has confirmed active exploitation and added it to the KEV catalog. The EPSS percentile of 96.4% reflects very high exploitation activity, driven by its use in exploit kit campaigns for target fingerprinting.
What products are affected by CVE-2016-3298?
CVE-2016-3298 affects the Microsoft Internet Messaging API as accessed through Internet Explorer. Multiple versions of Internet Explorer and Windows are affected. Internet Explorer has reached end of life and should be replaced.
How do I fix CVE-2016-3298?
Apply the Microsoft security update for CVE-2016-3298 and migrate away from Internet Explorer to a modern browser. See the Remediation section for additional hardening measures.
How severe is CVE-2016-3298?
CVE-2016-3298 is an information disclosure vulnerability with an EPSS percentile of 96.4%. While it does not directly enable code execution, its role as a reconnaissance tool in exploit kit campaigns makes it a significant component of multi-stage attacks targeting Internet Explorer users.
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