CVE-2020-0688 — Microsoft Exchange Validation Key Remote Code Execution Vulnerability

Executive Summary

A remote code execution vulnerability exists in Microsoft Exchange Server when the server fails to properly create unique keys at install time. Knowledge of a the validation key allows an authenticated user with a mailbox to pass arbitrary objects to be deserialized by the web application, which runs as SYSTEM. The security update addresses the vulnerability by correcting how Microsoft Exchange creates the keys during install.

Overview

8.8

CVSS HIGH

Important

MS Severity

Not Exploited

MS Exploit Status

More Likely

MS Exploit Likelihood

Category Remote Code Execution

Released Feb 11 2020

Last Updated Feb 11 2020

Publicly Disclosed No

CISA KEV Listed (added 2021-11-03)

Known Exploits None Known

EPSS Score 0.99965 — 0.99977 percentile

NVD CVSS 8.8 HIGH — differs from MSRC

CVSS Vector

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

ATTACK VECTOR

Network

ATTACK COMPLEXITY

Low

PRIVILEGES REQUIRED

Low

USER INTERACTION

None

SCOPE

Unchanged

EPSS Score

0.99965

probability of exploitation in the next 30 days

0.99977 percentile - updated 2026-08-14

View on FIRST.org

Affected Products

6 affected products

Product	KB Article	Severity	Impact	Restart Required
Microsoft Exchange Server 2010 Service Pack 3 Update Rollup 30	`4536989 (Security Update)`	Important	Remote Code Execution	Maybe
Microsoft Exchange Server 2013 Cumulative Update 23	`4536988 (Security Update)`	Important	Remote Code Execution	Maybe
Microsoft Exchange Server 2016 Cumulative Update 14	`4536987 (Security Update)`	Important	Remote Code Execution	Maybe
Microsoft Exchange Server 2016 Cumulative Update 15	`4536987 (Security Update)`	Important	Remote Code Execution	Maybe
Microsoft Exchange Server 2019 Cumulative Update 3	`4536987 (Security Update)`	Important	Remote Code Execution	Maybe
Microsoft Exchange Server 2019 Cumulative Update 4	`4536987 (Security Update)`	Important	Remote Code Execution	Maybe

Patches

3 patches

Article	Type	Restart
`4536989`	Security Update	Maybe
`4536988`	Security Update	Maybe
`4536987`	Security Update	Maybe

Exploits & PoC

15 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
zcgonvh/CVE-2020-0688	354	2020-03-01	Exploit and detect tools for CVE-2020-0688
Ridter/cve-2020-0688	328	2020-02-27	cve-2020-0688
random-robbie/cve-2020-0688	163	2020-02-25	cve-2020-0688
Yt1g3r/CVE-2020-0688_EXP	144	2020-02-27	CVE-2020-0688_EXP Auto trigger payload & encrypt method
Jumbo-WJB/CVE-2020-0688	66	2020-02-26	CVE-2020-0688 - Exchange
onSec-fr/CVE-2020-0688-Scanner	37	2020-02-28	Quick tool for checking CVE-2020-0688 on multiple hosts with a non-intrusive method.
w4fz5uck5/cve-2020-0688-webshell-upload-technique	23	2020-06-12	cve-2020-0688 UNIVERSAL Python implementation utilizing ASPX webshell for command output
MrTiz/CVE-2020-0688	21	2021-01-04	Remote Code Execution on Microsoft Exchange Server through fixed cryptographic keys
W01fh4cker/CVE-2020-0688-GUI	16	2024-05-09	GUI Exploit Tool for CVE-2020-0688(Microsoft Exchange default MachineKeySection deserialize vulnerability)
ravinacademy/CVE-2020-0688	11	2020-03-31	Exploitation Script for CVE-2020-0688 "Microsoft Exchange default MachineKeySection deserialize vulnerability"
zyn3rgy/ecp_slap	11	2020-10-23	CVE-2020-0688 PoC
youncyb/CVE-2020-0688	10	2020-02-28	CVE-2020-0688
cert-lv/CVE-2020-0688	8	2020-03-19	Vulnerability scanner for CVE-2020-0688
justin-p/PSForgot2kEyXCHANGE	5	2020-03-04	PoC for Forgot2kEyXCHANGE (CVE-2020-0688) written in PowerShell
murataydemir/CVE-2020-0688	4	2020-08-17	[CVE-2020-0688] Microsoft Exchange Server Fixed Cryptographic Key Remote Code Execution (RCE)

Detection Rules

Detection available

Community detection & vulnerability-scanning rules aggregated from Sigma and Nuclei templates. Validate and tune to your environment before deploying.