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HighVulnerabilityCVE-2026-96185updated 25 Oct 2026, 17:05 UTC

Microsoft Exchange Online: flaw could let a logged-in user run malicious code

A weakness in Microsoft's cloud email service could let someone who already has an account there run harmful code on Microsoft's servers. Microsoft manages the service, so most organizations have little to do beyond checking for official no

Official, 3 sources
SeverityHighCVSS 7.5 of 10
Being exploited?UnclearNo reports either way yet
Fix available?UnclearNo fixed version published in the sources yet
How sure is this?Official, 3 sourcesBacked by an official source

How the attack works simplified

  1. 1Authorized userAttacker already holds a valid account
  2. 2Crafted requestSent over the network to the service
  3. 3Buffer overflowStack memory overwritten by oversized input
  4. 4Code executionAttacker code runs on the service
  5. ResultAttacker runs code on Exchange Online

What happened

A stack-based buffer overflow in Microsoft Exchange Online allows an authorized attacker to execute code remotely over the network.

Why it is dangerous: A successful attacker could run code in Exchange Online, potentially affecting email data and the service's integrity for organizations using it.

Are you affected?

You are affected if your organization uses Microsoft Exchange Online (Microsoft 365 email) and has any authorized user account.

Microsoft Exchange Online (cloud service; no specific versions stated)

What to do

  1. Check Microsoft's advisory for CVE-2026-96185 for confirmation of service-side fixes
  2. Review Microsoft 365 admin center service notices and Exchange Online message center posts
  3. Limit account creation and review accounts with Exchange Online access

Timeline

  1. 22 Oct 2026, 14:00 UTC
    Publicly disclosed
  2. 22 Oct 2026, 14:00 UTC
    Reported by Microsoft MSRC · Microsoft MSRC
  3. 22 Oct 2026, 22:19 UTC
    Reported by NVD · NVD
  4. 25 Oct 2026, 17:05 UTC
    GitHub Advisory reported on it · GitHub Advisory

Sources 3 reports, oldest first

Official vendor, government CERT or advisory database

Technical details

ID
CVE-2026-96185 · GHSA-p369-hr2h-46vj
CVSS
7.5 / 10
EPSS
0.5% chance of exploitation within 30 days
Disclosed
22 Oct 2026, 14:00 UTC
On Zero Radar
before the radar started
Last change
25 Oct 2026, 17:05 UTC

The plain-language parts and the attack diagram were written by an AI model (anthropic/claude-haiku-5.5) from the sources above. Facts like versions, exploitation and dates come from the sources themselves. How Zero Radar works

Microsoft Exchange Online: flaw could let a logged-in user run malicious code · Zero Radar