VDB-186421 · CVE-2021-42321 · GCVE-0-2021-42321

Microsoft Exchange Server 2016 CU22/2019 CU11 privilege escalation

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
8.4	$0-$5k	0.00

Summaryinfo

A vulnerability marked as very critical has been reported in Microsoft Exchange Server 2016 CU22/2019 CU11. This issue affects some unknown processing. This manipulation causes an unknown weakness. This vulnerability is handled as CVE-2021-42321. The attack can be initiated remotely. Additionally, an exploit exists. Applying a patch is the recommended action to fix this issue.

Detailsinfo

A vulnerability has been found in Microsoft Exchange Server 2016 CU22/2019 CU11 (Groupware Software) and classified as very critical. As an impact it is known to affect confidentiality, integrity, and availability.

The weakness was released 11/09/2021 as confirmed security guidance (Website). The advisory is shared at portal.msrc.microsoft.com. This vulnerability is known as CVE-2021-42321. Technical details are unknown but a public exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 03/08/2025).

It is possible to download the exploit at packetstormsecurity.com. It is declared as attacked. We expect the 0-day to have been worth approximately $25k-$100k. The CISA Known Exploited Vulnerabilities Catalog lists this issue since 11/17/2021 with a due date of 12/01/2021:

Apply updates per vendor instructions.

Applying a patch is able to eliminate this problem. A possible mitigation has been published immediately after the disclosure of the vulnerability.

The vulnerability is also documented in the vulnerability database at Zero-Day.cz (677). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Type

Groupware Software

Vendor

Microsoft

Name

Exchange Server

Version

License

commercial

Website

Vendor: https://www.microsoft.com/

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 8.8
VulDB Meta Temp Score: 8.4

VulDB Base Score: 8.8
VulDB Temp Score: 8.4
VulDB Vector: 🔍
VulDB Reliability: 🔍

Vendor Base Score (Microsoft): 8.8
Vendor Vector (Microsoft): 🔍

NVD Base Score: 8.8
NVD Vector: 🔍

CNA Base Score: 8.8
CNA Vector (Microsoft): 🔍

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock

VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

NVD Base Score: 🔍

Exploitinginfo

Class: Privilege escalation
CWE: Unknown
CAPEC: 🔍
ATT&CK: 🔍

Physical: No
Local: No
Remote: Yes

Availability: 🔍
Access: Public
Status: Attacked
Download: 🔍

EPSS Score: 🔍
EPSS Percentile: 🔍

KEV Added: 🔍
KEV Due: 🔍
KEV Remediation: 🔍
KEV Ransomware: 🔍
KEV Notice: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Zero-Day.cz: 🔍

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Patch
Status: 🔍

Reaction Time: 🔍
0-Day Time: 🔍
Exposure Time: 🔍

Timelineinfo

10/12/2021 🔍
11/09/2021 +28 days 🔍
11/09/2021 +0 days 🔍
11/10/2021 +0 days 🔍
03/08/2025 +1214 days 🔍

Sourcesinfo

Vendor: microsoft.com

Advisory: portal.msrc.microsoft.com
Status: Confirmed

CVE: CVE-2021-42321 (🔍)
GCVE (CVE): GCVE-0-2021-42321
GCVE (VulDB): GCVE-100-186421
scip Labs: https://www.scip.ch/en/?labs.20161013

Entryinfo

Created: 11/10/2021 08:46
Updated: 03/08/2025 01:36
Changes: 11/10/2021 08:46 (34), 11/10/2021 08:49 (19), 11/12/2021 08:17 (2), 11/12/2021 08:20 (17), 04/22/2024 08:23 (29), 06/22/2024 16:27 (2), 06/23/2024 18:05 (2), 07/25/2024 01:11 (10), 09/16/2024 16:57 (1), 03/08/2025 01:36 (1)
Complete: 🔍
Cache ID: 216::103

If you want to get the best quality for vulnerability data then you always have to consider VulDB.