CVE-2015-2419: Microsoft Internet Explorer Memory Corruption Vulnerability

CVE-2015-2419 is a memory corruption vulnerability in Microsoft Internet Explorer’s JScript handling. A remote attacker who can lure a user to a crafted website may trigger code execution or a denial of service. Because the browser is commonly used for everyday web access, successful exploitation can give an attacker a foothold on the endpoint. Confirm all product and update details against the vendor advisory.

CISA lists the required action as applying updates per vendor instructions. Ransomware use of this CVE is not documented in the provided facts.

How it works

The weakness is classified as CWE-119 (improper restriction of operations within the bounds of a memory buffer). In this class of flaw, the browser’s JScript engine mishandles memory when processing certain web content. An attacker hosts or injects a malicious page that exercises the vulnerable code path; when the victim’s Internet Explorer renders that page, memory is corrupted. Depending on how the corruption is controlled, the result can be arbitrary code running in the context of the browser process or a crash that denies service.

No exploit mechanics, shellcode, or proof-of-concept details are provided in the facts; treat any public write-ups as unconfirmed until validated against the vendor advisory and your own lab testing. The attack surface is the browser itself when it encounters untrusted web content, so the primary vector is a user visiting a crafted site (or content loaded into an IE-based control).

Am I affected? How to find it in your systems

Internet Explorer has historically shipped with Windows client and server editions and may still be present even on systems that default to other browsers. Inventory every Windows endpoint and server for the presence of iexplore.exe and related IE components, including any applications that embed the IE rendering engine (WebBrowser control, older HTA hosts, or custom shells).

• Use software inventory or endpoint management tools to list installed IE versions and the Windows build they ride on; compare those versions to the fixed builds named in the Microsoft advisory for CVE-2015-2419.
• Check Group Policy and configuration baselines for any remaining dependence on IE or JScript in enterprise web apps, kiosks, or legacy line-of-business tools.
• Review proxy, DNS, and endpoint telemetry for unusual IE process launches, crashes of iexplore.exe, or navigation to unexpected external sites around the time of suspected activity. Memory-corruption exploitation often leaves little application-level logging, so pair process and network telemetry with crash dumps if available.
• Confirm whether Enhanced Protected Mode, 64-bit tabs, or other browser hardening features were enabled; these do not replace the patch but can change the exploitability surface.

If your inventory cannot map exact file or module versions, treat any unpatched IE installation as in-scope until the vendor advisory says otherwise.

How to remediate

Patch first. Apply the Microsoft security update that addresses CVE-2015-2419 exactly as described in the vendor advisory, then verify installation via your patch-management console or by checking file versions against the advisory’s documentation. Restart processes or systems if the advisory requires it so the updated binaries are loaded.

• After patching, re-scan the estate to confirm no residual vulnerable IE instances remain, including offline images, VDI gold images, and rarely used servers.
• Where IE is no longer required, disable or remove it per Microsoft guidance and move users and automated workflows to a supported modern browser.
• Enforce least privilege so that even a successful browser compromise runs with limited rights; keep users out of local administrator groups.
• Maintain application allow-listing and attack-surface reduction rules that constrain script hosts and child processes spawned from the browser.

If you can't patch immediately

When immediate patching is impossible, reduce exposure until the update can be deployed:

• Segment and restrict outbound web access for high-risk or unpatched hosts; force traffic through a filtering proxy that can block known-bad categories and newly registered domains.
• If a web application firewall or secure web gateway is in use, enable virtual-patching or signature sets that target IE memory-corruption patterns and generic drive-by behavior; tune to limit false positives.
• Disable or restrict JScript and Active Scripting for the Internet and Restricted Sites zones via Group Policy where business needs allow; note that this can break legitimate sites and must be tested.
• Move users to a different browser for daily work and limit IE to a short allow-list of internal sites, preferably in a sandboxed or remote-desktop session.
• Heighten monitoring: alert on IE crashes, unexpected child processes (cmd.exe, powershell.exe, wscript.exe, etc.), and anomalous network connections originating from iexplore.exe. Retain memory dumps for forensic review.
• Ensure EDR or antivirus is current and that behavioral protections against browser-based code execution are enabled.

These steps only buy time; they do not replace the vendor update.

If your data may have been exposed

Actively exploited browser vulnerabilities are a common path into endpoint compromise and subsequent data theft. If you have indicators that this CVE was used against your environment, follow your incident-response plan: isolate affected hosts, preserve evidence, credential-reset, and hunt for lateral movement. As a further check on whether personal or work email addresses have appeared in known breach corpora, individuals can run a free exposure scan of their email to review known breach data and then apply any needed password or MFA changes.