CVE-2018-8653
Microsoft Internet Explorer Scripting Engine Memory Corruption Vulnerability
Description
CVE-2018-8653 is a high-severity memory corruption vulnerability in the Microsoft Internet Explorer scripting engine. The vulnerability exists in how the scripting engine handles objects in memory, allowing an attacker to achieve remote code execution by convincing a user to visit a specially-crafted webpage. Internet Explorer versions 9, 10, and 11 are affected by this out-of-bounds write vulnerability. CISA has added this vulnerability to its Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. With an EPSS score of 22.99% (95.82nd percentile), CVE-2018-8653 presents a high probability of exploitation.
KEV Information
CVSS Score
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:HOpen in CalculatorAffected Products
| Vendor | Product | Version |
|---|---|---|
| microsoft | internet explorer | 9; 10; 11 |
Multiple CVSS Assessments
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
References
- http://www.securityfocus.com/bid/106255(Broken Link, Third Party Advisory, VDB Entry)
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2018-8653(Patch, Vendor Advisory)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2018-8653(US Government Resource)
Weakness Type
CWE-787: Out-of-bounds Write
An out-of-bounds write vulnerability occurs when software writes data past the end, or before the beginning, of the intended buffer. This can result in corruption of data, a crash, or code execution. In CVE-2018-8653, this weakness manifests in Internet Explorer's scripting engine (JScript), where improper handling of objects in memory allows an attacker to write beyond allocated memory boundaries, leading to memory corruption and ultimately remote code execution.
Learn more: CWE-787 — Out-of-bounds Write
Impact Analysis
CVE-2018-8653 carries a CVSS 3.1 score of 7.5 (HIGH), reflecting a significant but nuanced threat. The vulnerability is exploitable over the network, but the attack complexity is high, meaning specific conditions must be met for successful exploitation. No authentication is required, though user interaction is needed to visit a malicious webpage. Confidentiality (High): Successful exploitation can lead to complete disclosure of sensitive information on the affected system. Integrity (High): An attacker can fully modify data and install malicious software on the compromised system. Availability (High): Complete disruption of system availability is possible. The scope is unchanged, meaning the impact is confined to the Internet Explorer process and the user's session context. Organizations still running Internet Explorer 9, 10, or 11 face significant risk, particularly given the confirmed active exploitation in the wild.
Exploit Maturity
CVE-2018-8653 is confirmed as actively exploited through its listing in the CISA Known Exploited Vulnerabilities catalog. The EPSS score of 22.99% (95.82nd percentile) indicates a high probability of exploitation, placing this vulnerability well above the vast majority of CVEs in terms of exploitation likelihood. While the higher attack complexity reduces the ease of casual exploitation, the confirmed KEV status demonstrates that sophisticated threat actors have successfully weaponized this vulnerability. Federal agencies were required to remediate by 2022-05-03 per CISA's binding operational directive.
Remediation
- Apply vendor patches immediately as mandated by CISA KEV: Apply updates per vendor instructions. Microsoft released an out-of-band security update in December 2018 to address this vulnerability.
- Verify that all instances of Internet Explorer (versions 9, 10, and 11) across the organization have been updated to the patched version. Check Windows Update history to confirm the December 2018 cumulative security update is installed.
- As a strategic mitigation, transition away from Internet Explorer to a modern, supported browser such as Microsoft Edge, Google Chrome, or Mozilla Firefox, as Internet Explorer has reached end of life.
- If Internet Explorer must remain in use temporarily, configure Enhanced Protected Mode, restrict JScript execution through Group Policy, and limit browsing to trusted sites only using Internet Explorer's Zone settings.
- Monitor for indicators of compromise including unexpected Internet Explorer crashes, suspicious script execution, and unusual memory access patterns. Review proxy and firewall logs for connections to known malicious domains.
Technical Details
CVE-2018-8653 is a memory corruption vulnerability in Microsoft Internet Explorer's JScript scripting engine. The flaw is classified as an out-of-bounds write (CWE-787), where the scripting engine fails to properly handle objects in memory during script execution. When a user navigates to a specially-crafted webpage, the malicious script triggers the vulnerability, causing the engine to write data beyond the boundaries of an allocated memory buffer. The CVSS vector (CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H) reflects that while the vulnerability is network-exploitable, the high attack complexity indicates that the attacker must overcome specific memory layout conditions for reliable exploitation. This vulnerability affects the JScript engine across Internet Explorer 9, 10, and 11, and the unchanged scope means exploitation is limited to the context of the Internet Explorer process.
Frequently Asked Questions
Is CVE-2018-8653 being actively exploited?
Yes. CVE-2018-8653 is listed in the CISA Known Exploited Vulnerabilities catalog, confirming active exploitation in the wild. The EPSS score of 22.99% (95.82nd percentile) indicates a high probability of continued exploitation.
What products are affected by CVE-2018-8653?
CVE-2018-8653 affects Microsoft Internet Explorer versions 9, 10, and 11. The vulnerability is in the JScript scripting engine used by these browser versions on various Windows operating systems.
How do I fix CVE-2018-8653?
Apply the out-of-band security update released by Microsoft in December 2018. The recommended long-term solution is to migrate away from Internet Explorer to a modern browser, as Internet Explorer has reached end of life. If immediate migration is not possible, enable Enhanced Protected Mode and restrict JScript execution.
How severe is CVE-2018-8653?
CVE-2018-8653 has a CVSS 3.1 score of 7.5 (HIGH) with high impact across confidentiality, integrity, and availability. The EPSS score in the 95.82nd percentile indicates a significant exploitation probability, making this a high-priority vulnerability for remediation.
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