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

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CVSS Meta Temp Score
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CTI Interest Score
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8.6$0-$5k0.63

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 since 02/08/2021. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. 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 03/14/2021).

A public exploit has been developed by Jang (testanull) in Python and been published 2 weeks after the advisory. It is declared as functional. The exploit is shared for download at testbnull.medium.com. 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.

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CVSSv3infoedit

VulDB Meta Base Score: 9.3
VulDB Meta Temp Score: 8.6

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: 🔒

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

NVD Base Score: 🔒

Exploitinginfoedit

Class: Unknown
CWE: Unknown
ATT&CK: Unknown

Local: No
Remote: Yes

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

Price Prediction: 🔍
Current Price Estimation: 🔒

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Countermeasuresinfoedit

Recommended: Patch
Status: 🔍

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

Timelineinfoedit

02/08/2021 CVE assigned
03/02/2021 +22 days Advisory disclosed
03/02/2021 +0 days Countermeasure disclosed
03/03/2021 +0 days VulDB entry created
03/11/2021 +7 days Exploit disclosed
03/14/2021 +3 days VulDB last update

Sourcesinfoedit

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

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

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

Entryinfoedit

Created: 03/03/2021 08:22 AM
Updated: 03/14/2021 12:02 PM
Changes: (18) vulnerability_cvss3_nvd_av vulnerability_cvss3_nvd_ac vulnerability_cvss3_nvd_pr vulnerability_cvss3_nvd_ui vulnerability_cvss3_nvd_s vulnerability_cvss3_nvd_c vulnerability_cvss3_nvd_i vulnerability_cvss3_nvd_a vulnerability_cvss2_nvd_av vulnerability_cvss2_nvd_ac vulnerability_cvss2_nvd_au vulnerability_cvss2_nvd_ci vulnerability_cvss2_nvd_ii vulnerability_cvss2_nvd_ai vulnerability_cvss3_meta_basescore vulnerability_cvss3_meta_tempscore vulnerability_cvss2_nvd_basescore vulnerability_cvss3_nvd_basescore
Complete: 🔍
Committer: misc

Comments

misc (+1)
1 month 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)
1 month 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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