---
id: CVE-2026-87696
title: >-
  Improper verification of cryptographic signature in Microsoft Exchange Server
  allows an authorized attacker to elevate privileges over a network.
summary: >-
  Improper verification of cryptographic signature in Microsoft Exchange Server
  allows an authorized attacker to elevate privileges over a network.
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-347
published: '2026-10-13'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T04:18:52.363'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-87696'
references:
  - url: 'https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-87696'
    label: secure@microsoft.com
tags:
  - nvd
  - cve.org
ingestedAt: '2026-10-13T19:43:29.201Z'
vendor: Microsoft
product: Microsoft Exchange Server 2016 Cumulative Update 23
affected:
  - exchange_server_2016_cumulative_update_23 >= 15.01.0.0 < 15.01.2507.077
  - exchange_server_2019_cumulative_update_14 >= 15.02.0.0 < 15.02.1544.050
  - exchange_server_2019_cumulative_update_15 >= 15.02.0.0 < 15.02.1748.055
  - exchange_server_subscription_edition_rtm >= 15.02.0.0 < 15.02.2562.056
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-10-09T00:00:00+00:00'
epss: 0.00429
epssPercentile: 0.36971
---

## Overview

Improper verification of cryptographic signature in Microsoft Exchange Server allows an authorized attacker to elevate privileges over a network.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.