CVE-2010-0249 is an use-after-free vulnerability in Microsoft Internet Explorer. CISA added it to the Known Exploited Vulnerabilities catalogue on 20 May 2026, which means attackers have used it in real attacks. Microsoft Internet Explorer contains an use-after-free vulnerability that could allow remote attackers to execute arbitrary code by accessing a pointer associated with a deleted object.
What this vulnerability means in Internet Explorer
Use-after-free flaws occur when software keeps using a memory object after it has already been released. In a browser, that can turn routine page processing into an attacker-controlled memory corruption condition, because web content can influence timing, object lifetimes and code paths during rendering.
For Internet Explorer, the danger is not just that the browser crashes, but that the flaw can be shaped into remote code execution when malicious content reaches the vulnerable execution path. That is why use-after-free issues are treated as high-value browser exploitation bugs rather than ordinary stability defects.
Why this class of bug is dangerous
A deleted object pointer can become a gateway to arbitrary code execution if an attacker can reuse the freed memory with controlled data. In practice, that means a crafted page, script or embedded content may be able to influence what the browser later reads or executes, especially when the browser’s memory layout is predictable enough for exploitation.
Use-after-free weaknesses are especially serious in widely deployed browsers because the attack surface is exposed through ordinary user browsing. The victim does not need to install a file or run a program manually; a successful exploit can begin with a visit to hostile content.
External references are useful here: the CVE Program defines the record structure, while the NIST National Vulnerability Database is the standard place to confirm vulnerability metadata and track published details for the identifier.
How organisations assess exposure and likely impact
Exposure review starts with knowing where Internet Explorer still exists, whether it is enabled on endpoints, and whether users can reach untrusted content through it. Asset inventory matters because old browser components often survive inside legacy desktops, locked-down enterprise images or compatibility workflows long after they stop being the default browser.
Teams should also check vendor advisories and the CISA Known Exploited Vulnerabilities catalogue to understand whether the issue is being used in real-world attacks and to prioritise remediation accordingly. For broader prioritisation workflows, NHIMG’s Vulnerability Management Guide explains how asset scope, KEV awareness and remediation discipline fit together.
Where a browser bug is already exploited in the wild, impact analysis should assume more than a simple crash. The likely outcomes include code execution in the user context, follow-on payload delivery, and possible access to browser-stored data, session state or adjacent enterprise resources reachable from that workstation.
Remediation, detection and post-exploitation review
The first priority is to eliminate exposure to the vulnerable browser build or disable the affected path where a patch cannot yet be applied. When remediation is delayed, compensating controls should reduce the chance that hostile web content can reach the browser and limit what a successful exploit can do on the endpoint.
Detection should look for exploit delivery, unusual browser behaviour, suspicious child processes, unexpected script or memory activity, and signs that the endpoint executed code after web content was loaded. If exploitation is suspected, the review should extend beyond the browser itself to the host, because browser exploitation is often only the initial step in a wider intrusion chain.
Use-after-free exploitation also justifies a careful post-patch compromise review. If the flaw was actively abused, organisations should assume the endpoint may have been used to stage persistence, credential theft or lateral movement, and they should verify whether any local sessions or tokens were exposed during the event.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
MITRE ATT&CK addresses the attack and risk surface, while NIST SP 800-53 Rev 5, CIS Controls v8 and NIST CSF 2.0 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST SP 800-53 Rev 5 | SI-10 — Information Input Validation | Use-after-free exploitation depends on hostile input reaching the browser's parsing and execution path. |
| SI-16 — Memory Protection | This CVE is a memory-safety flaw that can be exploited through stale object pointers. | |
| Recommendation — Validate untrusted browser inputs and content processing paths to reduce exploitable memory-corruption conditions. Apply memory-protection and secure coding controls to reduce use-after-free exploitability. | ||
| CIS Controls v8 | CIS-7 — Continuous Vulnerability Management | The term is a KEV-listed vulnerability requiring prioritised exposure review and remediation. |
| Recommendation — Continuously inventory, prioritize and remediate KEV-listed browser vulnerabilities on exposed endpoints. | ||
| MITRE ATT&CK | T1203 — Exploitation for Client Execution | This browser flaw enables code execution through malicious client-side content. |
| Recommendation — Hunt for client-side exploitation activity and validate whether browser-delivered code executed on the endpoint. | ||
| NIST CSF 2.0 | DE.CM-01 — Networks and Network Services Monitored | Active exploitation requires monitoring for malicious browser traffic and endpoint symptoms. |
| Recommendation — Monitor browser and endpoint telemetry for signs of malicious content delivery and exploitation. | ||
Practitioner Guidance
Why practitioners should care: Browser memory-corruption bugs can become high-impact remote code execution paths, so exposure is determined less by the CVE label than by whether the vulnerable browser is still reachable on live systems.
What to watch for: Treat active exploitation indicators, repeated browser crashes around suspicious content, and unexpected process launches from the browser as signs that the issue may already have been weaponised.
Practitioner takeaway: For an exploited browser flaw, remediation is only the starting point, because endpoint review and session hygiene determine whether the compromise ends with the patch or continues after it.
Related resources from NHI Mgmt Group
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Reviewed and updated by the NHIMG editorial team on October 17, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org