CVE-2021-34523 — Microsoft Exchange Server Elevation of Privilege Vulnerability

Executive Summary

None

Overview

9

CVSS CRITICAL

Important

MS Severity

Not Exploited

MS Exploit Status

Less Likely

MS Exploit Likelihood

Category Elevation of Privilege

Released Jul 13 2021

Last Updated Jul 13 2021

Publicly Disclosed Yes

CISA KEV Listed (added 2021-11-03)

Known Exploits None Known

NVD CVSS 9 CRITICAL — matches MSRC

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N/E:U/RL:O/RC:C

ATTACK VECTOR

Local

ATTACK COMPLEXITY

Low

PRIVILEGES REQUIRED

None

USER INTERACTION

None

SCOPE

Changed

CONFIDENTIALITY

High

INTEGRITY

High

AVAILABILITY

None

EXPLOIT CODE MATURITY

Unproven

REMEDIATION LEVEL

Official Fix

REPORT CONFIDENCE

Confirmed

Temporal Score: 7.8

EPSS Score

No EPSS score available for this CVE.

View on FIRST.org

Affected Products

5 affected products

Product	KB Article	Severity	Impact	Restart Required
Microsoft Exchange Server 2013 Cumulative Update 23	`5001779 (Security Update)`	Important	Elevation of Privilege	Yes
Microsoft Exchange Server 2019 Cumulative Update 9	`5001779 (Security Update)`	Important	Elevation of Privilege	Yes
Microsoft Exchange Server 2016 Cumulative Update 20	`5001779 (Security Update)`	Important	Elevation of Privilege	Yes
Microsoft Exchange Server 2016 Cumulative Update 19	`5001779 (Security Update)`	Important	Elevation of Privilege	Yes
Microsoft Exchange Server 2019 Cumulative Update 8	`5001779 (Security Update)`	Important	Elevation of Privilege	Yes

Patches

1 patch

Article	Type	Restart
`5001779`	Security Update	Yes

Exploits & PoC

2 public PoCs

Unverified third-party code

Public proof-of-concept repositories aggregated from PoC-in-GitHub. They are not reviewed and may be incomplete, non-functional, or malicious — inspect the code before running anything.

Repository	Stars	Published	Description
mithridates1313/ProxyShell_POC	16	2021-10-02	POC for scanning ProxyShell(CVE-2021-34523,CVE-2021-34473,CVE-2021-31207)
SUPRAAA-1337/CVE-2021-34523	2	2023-09-02	test-yaml

Detection Rules

No public Sigma or Nuclei detection rule has been mapped to this CVE yet. Coverage is concentrated on exploited / high-profile vulnerabilities; check SigmaHQ for updates.

Acknowledgments

Orange Tsai(@orange_8361) from DEVCORE Research Team working with Trend Micro Zero Day Initiative

References

MSRC Advisory MITRE NVD