CVE-2021-34523KEV · OVERDUE

Microsoft Exchange Server Privilege Escalation Vulnerability

Critical · published July 14, 2021

Patch now

Confirmed exploited, and the score agrees

CVSS calls it critical at 9.0. It is confirmed in active exploitation. It sits in the 100.0th percentile for exploit probability.

1802
days past CISA
deadline
CVSS v3.1
9.0
EPSS
100%
Percentile
100.0
In the wild
Confirmed
What it is

🚨 The Exchange Server is a treasure chest, but this vulnerability is the map for thieves! An elevation of privilege flaw could let attackers grab the keys to your kingdom.🔥 Think of Microsoft Exchange Server like a high-security office building where a door was accidentally left ajar. An intruder could walk right in and access sensitive rooms without even buzzing in at reception, just because nobody checked the locks properly. An attacker exploiting this flaw could gain elevated privileges, allowing them to read, modify, or delete critical information and perform actions that could devastate your organization. Think of it as someone being able to suddenly access the CEO's office and tampering with sensitive documents. This is absolutely critical—don’t let them in!

Put simply

Think of Microsoft Exchange Server like a high-security office building where a door was accidentally left ajar. An intruder could walk right in and access sensitive rooms without even buzzing in at reception, just because nobody checked the locks properly. This vulnerability allows an authenticated attacker to elevate their privileges on an affected Microsoft Exchange Server, gaining unauthorized access to sensitive information or administrative capabilities.

What to do

An attacker exploiting this flaw could gain elevated privileges, allowing them to read, modify, or delete critical information and perform actions that could devastate your organization. Think of it as someone being able to suddenly access the CEO's office and tampering with sensitive documents. This is absolutely critical—don’t let them in! Patch your Microsoft Exchange Server immediately to the latest version (at least 15.2.1122.0 or later). Additionally, audit user roles and permissions to ensure no one has unnecessary access. Don't delay – the exploit is known and actively being used! You've got this! Stay vigilant, patch up, and you'll keep your digital fortress strong! 🛡️

The record
Technical detail
CVSS v3.1
9.0 · CRITICAL
Vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N
CVSS v4.0
Not supplied
EPSS
0.99990 · 100.0th percentile
Published
2021-07-14T22:15Z
KEV added
2021-11-03 · due 2021-11-17
Affected products (5)
ProductVersionsFixed in
microsoft/exchange_serverall versions—
microsoft/exchange_serverall versions—
microsoft/exchange_serverall versions—
microsoft/exchange_serverall versions—
microsoft/exchange_serverall versions—
References (5)
EPSS history
Timeline
  • 03 NOV 00:00Z
    Added to CISA KEV — remediate by Nov 17
    kev
  • 14 JUL 17:54Z
    Microsoft Exchange Server Elevation of Privilege Vulnerability
    cvelistv5