# CVE-2026-78459: Windows Internet Information Services heap buffer overflow

Source: https://junglewise.ai/threats/cve-2026-78459-heap-based-buffer-overflow-in-windows-internet-information  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-13. Updated: 2026-10-16  
License: CC BY 4.0 with a link back

CVE-2026-78459 · Severity: high · CVSS 7.8 · Published 2026-10-13

Windows Internet Information Services (IIS), which runs web applications on corporate servers, contains a heap buffer overflow vulnerability. An authorized attacker with local access could exploit this to gain elevated system privileges, potentially leading to full server compromise and access to hosted applications and data.

Technologies: [Microsoft Windows Internet Information Services](https://junglewise.ai/threats/technologies/windows-internet-information-services). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2026-78459 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-78459 being exploited in the wild.

**How severe is CVE-2026-78459?** High severity, with a CVSS score of 7.8, published 13 October 2026.

**Which products and versions are affected?** Microsoft Windows Internet Information Services.

**Is there a fix for CVE-2026-78459?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-78459 attacked?** It is attacked with local access, in a web application.

**Am I affected by CVE-2026-78459?** Check whether you run Microsoft Windows Internet Information Services. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A heap-based buffer overflow exists in Windows Internet Information Services, exploitable by an authenticated local attacker to achieve privilege escalation. The vulnerability requires prior local access and valid credentials, but allows an attacker to execute code with elevated privileges and potentially gain system-level control of the IIS server.

## Affected products

- Microsoft Windows Internet Information Services

## Timeline

- 2026-10-13: disclosed

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78459](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78459)

## Related threats

- [Microsoft Windows Internet Information Services race condition](https://junglewise.ai/threats/cve-2026-119961-concurrent-execution-using-shared-resource-with-improper)
- [Windows Internet Information Services integer underflow denial of service](https://junglewise.ai/threats/cve-2026-119936-integer-underflow-wrap-or-wraparound-in-windows-internet)
- [Microsoft Windows Internet Information Services stack buffer overflow](https://junglewise.ai/threats/cve-2026-70024-stack-based-buffer-overflow-in-windows-internet-information)