Is CVE-2010-0249 (Microsoft Internet Explorer Use-After-Free) being exploited in the wild?

What the CVE-2010-0249 answer means for exposure

This question is really about whether a specific browser weakness has moved from theoretical risk to confirmed exploitation. Because the answer says CISA added it to the KEV catalogue, the practical implication is that exposure is no longer a paper exercise: any environment still running the vulnerable browser path should be treated as active-risk until inventory, patching, or compensating controls prove otherwise.

For teams running legacy desktop estates, the first task is confirming whether Internet Explorer is still present, reachable, and usable on any managed system, kiosk, virtual desktop, or compatibility path. A vulnerability can remain operationally relevant even when it is not the primary browser, especially if enterprise settings, old web apps, or embedded components still invoke it.

Because this is a use-after-free, the issue sits in memory safety rather than a simple configuration mistake. That matters because exploitation can be opportunistic and content-driven, so the safest assumption is that browsing untrusted content through the affected path may be enough to trigger malicious code execution if an attacker can steer a victim to it.

How to reduce risk while patching is pending

The right response is to treat KEV inclusion as a prioritization signal, not just a vulnerability label. Align remediation with your vulnerability management process, and use the vendor advisory plus the CISA Known Exploited Vulnerabilities Catalog for the authoritative remediation context.

If immediate patching is not possible, remove the browser from practical use where you can, restrict access to untrusted websites, and harden the desktop path that can invoke it. In practice that may mean disabling legacy browser launch paths, tightening application control, limiting user privilege on affected endpoints, and segmenting systems that still need legacy access.

For Windows fleets that still depend on older browser behavior, this is also a dependency problem, not just a software update problem. A weak patch cadence, unsupported operating systems, or business-critical web applications tied to old rendering engines can extend the window of exposure well beyond the date a fix exists.

Use Vulnerability Management Guide to anchor the operational workflow for KEV triage, exception handling, and remediation tracking when browser exposure has to be prioritized against other competing fixes.

What to check for compromise and follow-on abuse

When an actively exploited browser flaw is involved, the question is not only whether the patch was applied, but whether the endpoint was already used as a delivery point for malware or credential theft. A browser exploit can be the entry point, after which the attacker may drop payloads, steal sessions, harvest secrets, or pivot to adjacent systems.

That is why the compromise check should focus on recent suspicious browser activity, unexpected child processes, new persistence mechanisms, unusual downloads, and signs that the endpoint executed code outside normal user workflows. If the system also stores credentials, saved sessions, or tokens, assume the blast radius may extend beyond the browser itself.

Teams that manage enterprise browsers should review whether the browser profile, password store, extension set, or saved session data could have been exposed. Enterprise Browser and Browser Security Guide is useful here because browser hardening and browser data exposure often determine whether an exploit becomes a broader account compromise.

For broader exploit context and post-compromise decision-making, Zero-Day and Exploited Vulnerabilities Guide covers the practical difference between urgent patching, emergency mitigation, and compromise assessment when exploitation is already believed to be happening.

Risk and Threat Considerations

Actively exploited browser vulnerabilities are attractive because they can turn normal web traffic into code execution on a user endpoint. That creates a narrow but serious failure mode: one vulnerable client can become the foothold for payload delivery, privilege escalation, credential theft, or lateral movement if the surrounding desktop controls are weak.

Failure mechanism: The attacker delivers malicious content that triggers the use-after-free condition, then uses the resulting execution to stage malware, steal data, or establish persistence before defenders notice the original browser event.

Impact: A successful exploit can expose the endpoint, the user’s authenticated sessions, and any reachable internal resources that the compromised workstation can access.

Practitioner Guidance

What to prioritise: Confirm where Internet Explorer or legacy rendering paths still exist, then rank those systems ahead of ordinary backlog work because KEV status means the exposure is already operationally relevant.

What to verify: Verify not only patch status, but also whether the endpoint was used recently for suspicious browsing, unexpected downloads, or browser-to-process behavior that would suggest post-exploit activity.

Decision rule: If the affected browser path cannot be removed immediately, treat the system as high priority for compensating controls and compromise review, not as a routine deferred patch.

Practitioner takeaway: Once a browser flaw appears in KEV, the real question becomes whether you can still trust the endpoint path that might have exposed it, not whether the browser is technically “obsolete.”

Related resources from NHI Mgmt Group

• How do you patch or mitigate CVE-2010-0249 (Microsoft Internet Explorer Use-After-Free)?
• Is CVE-2012-4792 (Microsoft Internet Explorer Use-After-Free) being exploited in the wild?
• Is CVE-2012-4969 (Microsoft Internet Explorer Use-After-Free) being exploited in the wild?
• CVE-2010-0249 (Microsoft Internet Explorer Use-After-Free)