Microsoft Exchange Server 2013 CU23/2016 CU18/2016 CU19/2019 CU7/2019 CU8 ProxyLogon unknown vulnerability

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 (≈)
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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.
8.9$0-$5k0.03

A vulnerability was found in Microsoft Exchange Server 2013 CU23/2016 CU18/2016 CU19/2019 CU7/2019 CU8 (Groupware Software). It has been classified as very critical. This is going to have an impact on confidentiality, and integrity.

The weakness was disclosed 03/02/2021 as confirmed security guidance (Website). The advisory is shared for download at portal.msrc.microsoft.com. This vulnerability is traded as CVE-2021-26855. Technical details are unknown but a public exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 12/13/2021).

A public exploit has been developed by Jang (testanull) in Python and been published 2 weeks after the advisory. The exploit is shared for download at testbnull.medium.com. It is declared as functional. As 0-day the estimated underground price was around $25k-$100k.

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

Productinfo

Type

Vendor

Name

Version

License

CPE 2.3info

CPE 2.2info

Video

Youtube: Not available anymore

CVSSv4info

VulDB CVSS-B Score: 🔍
VulDB CVSS-BT Score: 🔍
VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 9.3
VulDB Meta Temp Score: 8.9

VulDB Base Score: 9.1
VulDB Temp Score: 8.4
VulDB Vector: 🔍
VulDB Reliability: 🔍

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

NVD Base Score: 9.8
NVD Vector: 🔍

CVSSv2info

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

NVD Base Score: 🔍

Exploitinginfo

Class: Unknown
CWE: Unknown
ATT&CK: Unknown

Local: No
Remote: Yes

Availability: 🔍
Access: Public
Status: Functional
Author: Jang (testanull)
Programming Language: 🔍
Download: 🔍

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

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Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Patch
Status: 🔍

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

Timelineinfo

02/08/2021 🔍
03/02/2021 +22 days 🔍
03/02/2021 +0 days 🔍
03/03/2021 +0 days 🔍
03/11/2021 +7 days 🔍
12/13/2021 +277 days 🔍

Sourcesinfo

Vendor: microsoft.com

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

CVE: CVE-2021-26855 (🔍)
scip Labs: https://www.scip.ch/en/?labs.20161013

Entryinfo

Created: 03/03/2021 08:22
Updated: 12/13/2021 11:23
Changes: 03/03/2021 08:22 (33), 03/03/2021 08:25 (19), 03/06/2021 12:17 (2), 03/12/2021 07:43 (9), 03/14/2021 12:02 (18), 12/13/2021 11:23 (2)
Complete: 🔍
Committer: misc

Discussion

misc (+1)
3 years ago
Nmap script from Microsoft to detect if an Exchange Server is vulnerable: https://github.com/microsoft/CSS-Exchange/blob/main/Security/http-vuln-cve2021-26855.nse
misc (+0)
3 years ago
There are 2 different exploits at the moment, one written in python and another in go. The exploit code of Jang was removed by GitHub, and was later made available on Web Archive and GitLab. Here are two links to the exploit code: https://git.blackmarble.sh/backup/proxyLogon/-/blob/main/PoC_proxyLogon.py and https://github.com/h4x0r-dz/CVE-2021-26855.

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