Key points
- CVE-2026-70024 affects Windows Internet Information Services with a CVSS score of 9.8.
- The vulnerability is a stack-based buffer overflow enabling unauthorized remote code execution.
- Microsoft has released an official security advisory for this critical severity issue.
Microsoft has published a security advisory for CVE-2026-70024, a critical vulnerability in Windows Internet Information Services. This flaw allows unauthenticated attackers to execute arbitrary code remotely via a network request.
What happened
Microsoft’s Security Update Guide identifies CVE-2026-70024 as a remote code execution vulnerability within Windows Internet Information Services. The flaw stems from a stack-based buffer overflow, a condition where data exceeds the memory space allocated for it. According to the National Vulnerability Database, this issue carries a CVSS score of 9.8, placing it in the critical severity category. The weakness is classified under CWE-20 and CWE-121. An unauthorized attacker can exploit this flaw over a network to run malicious code on the affected server. No specific version numbers are listed in the provided advisory text, but the impact applies to the IIS service generally.
Why it matters
Remote code execution in a web server component like IIS presents a severe risk to organisational infrastructure. Attackers do not need prior authentication to attempt exploitation, as the vulnerability is accessible over the network. A successful exploit allows an attacker to execute code over a network. The high CVSS score reflects the critical severity rating assigned by the National Vulnerability Database. Security teams must treat this as an operational concern based on the critical rating.
What happens next
- Verify if your infrastructure hosts Windows Internet Information Services.
- Consult internal asset inventories to identify all servers running affected IIS versions.
- Monitor Microsoft’s update guide for the specific patch release corresponding to CVE-2026-70024.
- Prepare deployment plans to apply the fix as soon as it becomes available.
Patch priority
Teams usually prioritise systems exposed to the public internet for immediate remediation. Check whether your IIS servers are directly accessible from external networks. Apply patches to these high-exposure assets first. Test the update in a non-production environment to ensure stability. Back up configurations before making changes. Roll out the fix in stages to minimise disruption. Monitor logs for any unusual activity during the update process. Ensure that rollback procedures are ready in case the update causes issues.
Background: Remote code execution vulnerabilities
Remote code execution often occurs because developers trust user input without validation, fail to restrict file permissions, or neglect to update dependencies. Fix these errors by enforcing strict input sanitisation, applying least-privilege principles, and integrating automated security checks into your secure software development lifecycle to prevent arbitrary command execution.
Read the full guide: Seven Configuration Mistakes That Allow Remote Code Execution
What to do and how to stay safe: Microsoft
- Audit your network for all instances of Windows Internet Information Services.
- Restrict external access to IIS ports using firewalls or network segmentation.
- Monitor server logs for signs of exploitation attempts or unusual traffic patterns.
- Wait for the vendor to provide an official update before applying any changes.
Step-by-step guide: Patch Management: Definition, Purpose and Operational Reality
General security guidance from the AppSec Scoop newsroom. It is not confirmed advice from the organisations named in this story.
Frequently asked questions
What is CVE-2026-70024?
It is a critical remote code execution vulnerability in Windows Internet Information Services caused by a stack-based buffer overflow.
How severe is this vulnerability?
The National Vulnerability Database rates CVE-2026-70024 as critical with a CVSS score of 9.8.
Can attackers exploit this remotely?
Yes, an unauthorised attacker can execute code over a network without prior authentication.
