CVE-2020-0968 is a scripting engine memory corruption vulnerability in Microsoft Internet Explorer. CISA added it to the Known Exploited Vulnerabilities catalogue on 3 November 2021, which means attackers have used it in real attacks. Microsoft Internet Explorer contains a memory corruption vulnerability due to how the Scripting Engine handles objects in memory, leading to remote code execution.
Why this vulnerability is dangerous in a browser scripting engine
A scripting engine memory corruption flaw is serious because the browser process often runs with the user’s trust and can be reached through ordinary web content. When malformed objects or memory state let an attacker trigger remote code execution, a simple visit to a malicious page can become a full system compromise path.
That danger is amplified in legacy browser components because they sit close to rich parsing, scripting, and rendering logic. The issue is not just that code can crash, but that corruption can be shaped into attacker-controlled execution before the user notices anything unusual.
How organisations should assess exposure
Exposure checks start with asset inventory, because the question is not only whether Internet Explorer exists somewhere, but whether it is installed, enabled, or still reachable through compatibility mode, embedded workflows, or old enterprise images. Organisations should also check whether endpoints can reach the public internet, whether the browser is used in privileged sessions, and whether the vendor advisory and the CISA KEV catalogue confirm that the issue is being actively exploited.
For a CVE like this, authoritative version and patch details belong in the vendor advisory and KEV listing rather than in a glossary entry. The CVE Program and NIST National Vulnerability Database are the best starting points for record validation and cross-checking.
Remediation and compensating controls
Memory corruption bugs are usually fixed by vendor patching, but browsers and legacy components often create timing and compatibility constraints that delay deployment. Where patching cannot happen immediately, organisations should reduce exposure by removing unnecessary access to the affected browser path, limiting internet-facing use cases, and isolating high-risk browsing activity from sensitive credentials and administrative work.
Because the primary concern is remote code execution, compensating controls should focus on containment, not just detection. A vulnerable browser should not be treated as a harmless utility if it remains available to users who handle sensitive data or elevated sessions.
Detection and post-exploitation review
After exploitation, defenders should look for signs of abnormal browser behaviour, unexpected child processes, suspicious script activity, and follow-on payload execution. Memory corruption exploitation often blends into normal browsing until the attacker gains a foothold, so endpoint telemetry and process lineage matter more than page content alone.
If there is evidence of successful compromise, review the affected host for secondary persistence, browser-download artefacts, and any credentials, sessions, or tokens exposed during the attack. A browser exploit can be the entry point for broader endpoint compromise, not the end state.
Risk and Threat Considerations
This vulnerability matters because actively exploited browser memory corruption can turn a routine web visit into remote code execution. The threat is highest on endpoints that still depend on legacy browser functionality, accept untrusted web content, or are used in sessions with access to sensitive systems.
Failure mechanism: The attacker abuses corrupted in-memory object handling to steer execution flow, load malicious code, or stage a second payload after initial browser compromise.
Impact: Successful exploitation can lead to endpoint takeover, credential theft, lateral movement, and a wider incident if the compromised host has access to privileged resources or internal services.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
NIST SP 800-53 Rev 5 provides the primary governance reference for this term.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST SP 800-53 Rev 5 | SI-2 — Flaw Remediation | CVE exploitation requires timely remediation of the browser flaw. |
| RA-5 — Vulnerability Monitoring and Scanning | Exposure assessment depends on finding systems that still run the affected software path. | |
| SI-3 — Malicious Code Protection | Exploitation turns a browser session into a code-execution path that malware controls. | |
| Recommendation — Prioritise SI-2 to patch the vulnerable browser component and verify remediation on exposed endpoints. Use RA-5 to identify endpoints and images that still expose the vulnerable browser engine. Apply SI-3 to block and detect malicious payloads delivered through browser compromise. | ||
Practitioner Guidance
Why practitioners should care: Treat this kind of CVE as an exposure management problem, not only a patching task. The practical question is which systems still expose the vulnerable browser path and whether those systems have enough containment to limit blast radius if exploitation occurs.
What to watch for: Prioritise systems where the browser is still operational for business reasons, especially where users browse externally while signed into high-value accounts or where endpoint visibility is weak. Those are the environments where a browser RCE is most likely to become a meaningful security incident.
Related resources from NHI Mgmt Group
- CVE-2020-0674 (Microsoft Internet Explorer Scripting Engine Memory Corruption)
- CVE-2018-8653 (Microsoft Internet Explorer Scripting Engine Memory Corruption)
- CVE-2019-1367 (Microsoft Internet Explorer Scripting Engine Memory Corruption)
- CVE-2020-0878 (Microsoft Edge and Internet Explorer Memory Corruption)