External risk intelligence

Windows IIS Stack Buffer Overflow Remote Code Execution.

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-70024

Windows Internet Information Services (IIS) is a web server platform designed to host web applications and content. It is a core component typically deployed as an internet-facing public web server or API endpoint, making it public-facing by design in normal use.

Buffer Overflow

Halo Surface Signal: 5 out of 5 — more likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This vulnerability impacts Windows Internet Information Services, a common web server technology. It allows attackers to potentially execute code remotely without authentication, which could lead to a broad compromise of affected systems. The main concern is to confirm if our environment utilizes this specific technology and assess the potential exposure.

Remote attackers can run unauthorized code.
Critical vulnerability in common web server.
Confirm relevance and potential exposure.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by sending specially crafted network requests to an exposed Windows Internet Information Services (IIS) web server. If the server is configured with the vulnerable component, these requests could trigger a buffer overflow, allowing the attacker to execute arbitrary code on the server.

No authentication or privileges required.
Network-based requests trigger overflow.
Enables remote code execution.

Live Threat

Current exploitation, exposure, and threat context

Windows Internet Information Services (IIS) could be at risk of code execution over a network, potentially affecting system data and service behavior. This vulnerability may allow an unauthorized attacker to execute arbitrary code when supported by the advisory, impacting the integrity and availability of the affected server.

System data and service behavior.
Network code execution.
Unauthorized code execution.

Operational Fix

Recommended remediation, mitigation, and detection steps

Given that this vulnerability affects Windows Internet Information Services (IIS), ownership likely falls to infrastructure or platform teams responsible for web services, with collaboration from network and security teams for exposure and remediation planning. The first practical step is to identify all IIS instances, confirm their external reachability and business criticality, and then engage the accountable owner to prioritize and schedule the fix, potentially through vendor coordination or by implementing temporary risk reduction measures if immediate patching is not feasible.

Infrastructure/platform teams should own resolution.
Verify external reachability and business criticality.
Plan remediation based on risk and availability.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is Windows Internet Information Services (IIS)?

IIS is a flexible, secure, and manageable web server from Microsoft used to host websites, services, and applications. It acts as the underlying platform that processes HTTP requests and manages web content delivery. Because it is often installed on Windows Server to provide public-facing web interfaces or API endpoints, it is a frequent target for network-based threats.

What does a stack-based buffer overflow mean in CVE-2026-70024?

This vulnerability involves a memory corruption weakness (CWE-121) where the application writes more data to a temporary memory space than it can hold. Because the software fails to properly validate the input (CWE-20), the extra data overflows into adjacent memory. In this case, an attacker can use this flaw to overwrite critical system instructions, potentially running their own unauthorized code on the host server.

How is this vulnerability triggered by an attacker?

An attacker triggers this bug by sending a specially crafted request over the network to a vulnerable IIS server. It is important to note that the attacker does not need any valid user account or special system privileges to initiate the attack. Normal requests that follow standard web protocols do not trigger the overflow; only packets specifically designed to exploit the memory handling flaw pose a risk.

Is my server at risk if it runs IIS?

According to Halo Surface Signal, IIS is typically deployed as an internet-facing public web server or API endpoint, making it highly relevant to this advisory. If your server is accessible from the public internet, it faces a higher level of risk because attackers can reach the vulnerable component directly. Internal-only servers may be at lower risk, though they remain vulnerable if an attacker gains access to your internal network.

How should I respond to this CVE?

Start by identifying every instance of IIS running within your infrastructure to build an accurate inventory. Once identified, evaluate each server based on its business criticality and network reachability. Coordinate with your infrastructure or platform teams to prioritize these servers for updates. If immediate patching is not possible, explore temporary risk-reduction configurations to limit access to these services until the fix is applied.

References

msrc.microsoft.com/update-guide/vulnerability/CVE-2026-70024

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.