# CVE-2026-55007 — Microsoft Exchange Server 2019 Cumulative Update 14

> As of 2026-10-08, CVE-2026-55007 is a HIGH-severity vulnerability in Microsoft Exchange Server 2019 Cumulative Update 14, CVSS v3.1 8.1, EPSS 0.7% (52.0th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-55007, 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-2026-55007?

Double free in Microsoft Exchange Server allows an unauthorized attacker to execute code over a network.

The record classifies CVE-2026-55007 under weakness class [CWE-415](https://intel.threadlinqs.com/cwe/CWE-415). 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:** 8.1 — HIGH (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C`)
- **EPSS (FIRST):** 0.7% probability of exploitation in the next 30 days, higher than 52.0% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 6.1/10 — 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-2026-55007 being exploited?

It currently carries a trending score of 40 in the Threadlinqs vulnerability feed.

## Affected products and versions

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

## How to fix CVE-2026-55007

No vendor patch reference has been recorded for CVE-2026-55007 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-2026-55007

1 tracked threat in the Threadlinqs corpus references CVE-2026-55007, 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

## Sources

Enriched from CVE.org, FIRST EPSS, GitHub Security Advisories. 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-2026-55007)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-55007
Full detection coverage and IOCs for threats exploiting CVE-2026-55007 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp