# CVE-2026-96940 — Microsoft Exchange Server 2016 Cumulative Update 23

> As of 2026-10-08, CVE-2026-96940 is a HIGH-severity vulnerability in Microsoft Exchange Server 2016 Cumulative Update 23, CVSS v3.1 8.8, EPSS 0.4% (40.6th percentile). Threadlinqs Intelligence links 2 tracked threat campaigns to CVE-2026-96940, most recently “October 2026 Microsoft Patch Tuesday: Exploited Windows Shell MotW Bypass (CVE-2026-96951), 1,417 Vulnerabilities Patched”.

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

## What is CVE-2026-96940?

An elevation of privilege vulnerability exists when Microsoft Exchange Outlook Web Access (OWA) fails to properly handle web requests. An attacker who successfully exploited this vulnerability could perform script/content injection attacks and attempt to trick the user into disclosing sensitive information. To exploit the vulnerability, an attacker could send a specially crafted email message containing a malicious link to a user. Alternatively, an attacker could use a chat client to social engineer a user into clicking the malicious link. The security update addresses the vulnerability by correcting how Microsoft Exchange validates web requests. Note: In order to exploit this vulnerability, a user must click a maliciously crafted link from an attacker.

The record classifies CVE-2026-96940 under weakness class [CWE-1390](https://intel.threadlinqs.com/cwe/CWE-1390). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs low-privilege credentials, needs no user interaction, and has high impact on confidentiality, integrity, availability. 4 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 23 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 8.8 — HIGH (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C`)
- **EPSS (FIRST):** 0.4% probability of exploitation in the next 30 days, higher than 40.6% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 8/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-10-02, last modified 2026-10-08

## Is CVE-2026-96940 being exploited?

Weaponised exploit code for CVE-2026-96940 is publicly available. 1 public proof-of-concept repository is tracked for this identifier. It currently carries a trending score of 51 in the Threadlinqs vulnerability feed.

- [HORKimhab/CVE-2026-96940](https://github.com/HORKimhab/CVE-2026-96940) (github)

## Affected products and versions

- [Microsoft](https://intel.threadlinqs.com/vendors/microsoft): Exchange Server 2016 Cumulative Update 23, Exchange Server 2019 Cumulative Update 14, Exchange Server 2019 Cumulative Update 15, Exchange Server Subscription Edition RTM

## How to fix CVE-2026-96940

No vendor patch reference has been recorded for CVE-2026-96940 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-96940

2 tracked threats in the Threadlinqs corpus reference CVE-2026-96940, either in the campaign’s CVE list or as an indicator on the campaign record.

- [October 2026 Microsoft Patch Tuesday: Exploited Windows Shell MotW Bypass (CVE-2026-96951), 1,417 Vulnerabilities Patched](https://intel.threadlinqs.com/threat/TL-2026-3443) — CRITICAL · 2026-10-13
- [Microsoft Reissues September 2026 Exchange Server Updates (V2) for CVE-2026-96940 Mailbox Authorization Flaw](https://intel.threadlinqs.com/threat/TL-2026-2864) — HIGH · 2026-10-03

## Sources

Enriched from CVE.org, FIRST EPSS, public proof-of-concept repositories. Last verified by Threadlinqs on 2026-10-10.

**Vendor advisory and patch**

- [msrc.microsoft.com — vendor advisory](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-96940)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-96940
Full detection coverage and IOCs for threats exploiting CVE-2026-96940 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp