# CVE-2026-66302 — Microsoft Skype for Business Server 2015 CU13

> As of 2026-10-08, CVE-2026-66302 is a CRITICAL-severity vulnerability in Microsoft Skype for Business Server 2015 CU13, CVSS v3.1 9.8, EPSS 0.9% (60.9th percentile). Threadlinqs Intelligence links 2 tracked threat campaigns to CVE-2026-66302, most recently “September 2026 Microsoft Patch Tuesday — Record 966+ Vulnerabilities with Two Actively Exploited Zero-Days (CVE-2026-81963, CVE-2026-85880) and Multiple Critical Wormable RCEs”.

**Last updated:** 2026-10-08

## What is CVE-2026-66302?

External control of file name or path in Skype for Business allows an unauthorized attacker to execute code over a network.

The record classifies CVE-2026-66302 under weakness class [CWE-73](https://intel.threadlinqs.com/cwe/CWE-73). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity, availability. 3 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 52 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 9.8 — CRITICAL (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C`)
- **EPSS (FIRST):** 0.9% probability of exploitation in the next 30 days, higher than 60.9% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 7.3/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-09-08, last modified 2026-10-08

## Is CVE-2026-66302 being exploited?

It currently carries a trending score of 47 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [Microsoft](https://intel.threadlinqs.com/vendors/microsoft): Skype for Business Server 2015 CU13, Skype for Business Server 2019 CU8, Skype for Business Server Subscription Edition CU1

## How to fix CVE-2026-66302

The record marks a vendor fix as available for CVE-2026-66302. Patch reference: [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66302](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66302). Vendor advisory: [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66302](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66302). Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.

## Threat activity tracking CVE-2026-66302

2 tracked threats in the Threadlinqs corpus reference CVE-2026-66302, either in the campaign’s CVE list or as an indicator on the campaign record.

- [September 2026 Microsoft Patch Tuesday — Record 966+ Vulnerabilities with Two Actively Exploited Zero-Days (CVE-2026-81963, CVE-2026-85880) and Multiple Critical Wormable RCEs](https://intel.threadlinqs.com/threat/TL-2026-2398) — CRITICAL · 2026-09-08
- [Microsoft September 2026 Patch Tuesday — 999 CVEs, 3 actively exploited zero-days (CVE-2026-85880, CVE-2026-81963, CVE-2026-85046)](https://intel.threadlinqs.com/threat/TL-2026-2407) — CRITICAL · 2026-09-08

## Sources

Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories. Last verified by Threadlinqs on 2026-10-10. This product uses the NVD API but is not endorsed or certified by the NVD.

**Vendor advisory and patch**

- [msrc.microsoft.com — vendor advisory](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66302)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-66302
Full detection coverage and IOCs for threats exploiting CVE-2026-66302 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp