CVE-2020-0688Known exploitationPublic exploitNetwork attack vector

SYSTEM code execution via static ViewState keys

Published Feb 11, 2020 · Updated Oct 21, 2025

Remote code execution in Microsoft Exchange 2010 SP3, 2013 CU23, 2016 CU14-CU15, and 2019 CU3-CU4 allows remote authenticated users to run code. ECP uses identical validationKey and decryptionKey values across installations, so forged signed __VIEWSTATE data is accepted and deserialized. Any mailbox account can obtain its session values, submit a gadget payload, and execute arbitrary .NET code as SYSTEM.

CVSS severity8.8
High
EPSS probability99.97%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Remote code execution in Microsoft Exchange 2010 SP3, 2013 CU23, 2016 CU14-CU15, and 2019 CU3-CU4 allows remote authenticated users to run code. ECP uses identical validationKey and decryptionKey values across installations, so forged signed __VIEWSTATE data is accepted and deserialized. Any mailbox account can obtain its session values, submit a gadget payload, and execute arbitrary .NET code as SYSTEM.

The record

CVE
CVE-2020-0688
Published
Feb 11, 2020
Updated
Oct 21, 2025
Vendor
Microsoft
Product
Microsoft Exchange Server 2013
Classifications
CWE-287, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 11, 2020CVE publishedPublication date reported by the CVE source.
  2. Oct 21, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=Cumulative Update 23

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Microsoft · Microsoft Exchange Server 2013version=Cumulative Update 23
Microsoft · Microsoft Exchange Server 2019 Cumulative Update 4version=unspecified
Microsoft · Microsoft Exchange Server 2019 Cumulative Update 3version=unspecified
Microsoft · Microsoft Exchange Server 2010 Service Pack 3version=unspecified
Microsoft · Microsoft Exchange Server 2016 Cumulative Update 14version=unspecified
Microsoft · Microsoft Exchange Server 2016 Cumulative Update 15version=unspecified

Published CVSS scores

8.8CISA ADP VulnrichmentCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
9.0NIST NVDAV:N/AC:L/Au:S/C:C/I:C/A:C
8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationReported
Public exploitPublished

Weakness, pattern, technique

CWE-287Improper Authentication
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Reported exploitation

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo