VDB-178577 · CVE-2021-34473 · GCVE-0-2021-34473

Microsoft Exchange Server up to 2019 CU9 ProxyShell server-side request forgery

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.
9.1	$5k-$25k	0.00

Summaryinfo

A vulnerability was found in Microsoft Exchange Server 2013 CU23/2016 CU19/2016 CU20/2019 CU8/2019 CU9. It has been rated as very critical. This vulnerability affects unknown code. The manipulation leads to an unknown weakness. This vulnerability is uniquely identified as CVE-2021-34473. The attack is possible to be carried out remotely. Moreover, an exploit is present. It is suggested to install a patch to address this issue.

Detailsinfo

A vulnerability was found in Microsoft Exchange Server 2013 CU23/2016 CU19/2016 CU20/2019 CU8/2019 CU9 (Groupware Software). It has been rated as very critical. Using CWE to declare the problem leads to CWE-918. The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. Impacted is confidentiality, integrity, and availability.

The weakness was disclosed 07/13/2021 as confirmed security guidance (Website). The advisory is shared at portal.msrc.microsoft.com. The identification of this vulnerability is CVE-2021-34473. Technical details are unknown but an exploit is available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 10/29/2025).

It is declared as attacked. The CISA Known Exploited Vulnerabilities Catalog lists this issue since 11/03/2021 with a due date of 11/17/2021:

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.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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: 9.5
VulDB Meta Temp Score: 9.1

VulDB Base Score: 9.8
VulDB Temp Score: 9.4
VulDB Vector: 🔍
VulDB Reliability: 🔍

Vendor Base Score (Microsoft): 9.1
Vendor Vector (Microsoft): 🔍

NVD Base Score: 9.8
NVD Vector: 🔍

CNA Base Score: 9.1
CNA Vector (Microsoft): 🔍

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
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Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
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VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

NVD Base Score: 🔍

Exploitinginfo

Class: Server-side request forgery
CWE: CWE-918
CAPEC: 🔍
ATT&CK: 🔍

Physical: No
Local: No
Remote: Yes

Availability: 🔍
Status: Attacked

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

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Patch
Status: 🔍

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

Timelineinfo

06/09/2021 🔍
07/13/2021 +34 days 🔍
07/13/2021 +0 days 🔍
07/14/2021 +0 days 🔍
10/29/2025 +1568 days 🔍

Sourcesinfo

Vendor: microsoft.com

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

CVE: CVE-2021-34473 (🔍)
GCVE (CVE): GCVE-0-2021-34473
GCVE (VulDB): GCVE-100-178577
scip Labs: https://www.scip.ch/en/?labs.20161013

Entryinfo

Created: 07/14/2021 08:52
Updated: 10/29/2025 19:25
Changes: 07/14/2021 08:52 (33), 07/14/2021 08:56 (20), 07/17/2021 14:12 (2), 12/13/2021 11:27 (1), 04/21/2024 20:19 (29), 07/26/2024 21:49 (28), 09/15/2024 13:07 (2), 10/29/2025 19:25 (1)
Complete: 🔍
Cache ID: 216::103