Exploited vulnerability · CISA KEV

Is CVE-2020-0688 exploited? Yes: in CISA KEV since 3 Nov 2021

Gociux · Microsoft Exchange Server · data: CISA KEV, CVE record, FIRST EPSS

Yes. CVE-2020-0688, Microsoft Exchange Server Validation Key Remote Code Execution Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 3 Nov 2021, 631 days after it was published. It is known to be used in ransomware campaigns. It affects Microsoft Exchange Server. If you run it, CISA's required action is: Apply updates per vendor instructions.

exploitedYesCISA KEV · 3 Nov 2021

ransomwareKnownused in campaigns

EPSStop 1%among the most likely CVEs to be exploited

severity8.8CVSS 3.1 · high

US federal due3 May 2022BOD 22-01 deadline

What it is

Microsoft Exchange Server Validation Key fails to properly create unique keys at install time, allowing for remote code execution.

Vendor	Microsoft (391 exploited CVEs in KEV)
Product	Exchange Server
Vulnerability	Microsoft Exchange Server Validation Key Remote Code Execution Vulnerability
Weakness	CWE-287
Published	11 Feb 2020
Added to KEV	3 Nov 2021
Reported by (CNA)	microsoft

What to do

Check whether you run it. Look for Exchange Server in your asset inventory, including appliances and cloud images. Stack check lists every exploited Microsoft CVE at once.
Apply the fix. Apply updates per vendor instructions.
If you can't patch today, take the affected service off the internet or restrict who can reach it, and check its logs for signs of compromise since 11 Feb 2020.
Get told next time. Email alerts when CISA adds a CVE for Microsoft.

Other exploited CVEs in Exchange Server

CVE-2023-21529: Microsoft Exchange Server Deserialization of Untrusted Data Vulnerability (13 Apr 2026)
CVE-2021-31196: Microsoft Exchange Server Information Disclosure Vulnerability (21 Aug 2024)
CVE-2024-21410: Microsoft Exchange Server Privilege Escalation Vulnerability (15 Feb 2024)
CVE-2022-41080: Microsoft Exchange Server Privilege Escalation Vulnerability (10 Jan 2023)
CVE-2022-41082: Microsoft Exchange Server Remote Code Execution Vulnerability (30 Sep 2022)
CVE-2022-41040: Microsoft Exchange Server Server-Side Request Forgery Vulnerability (30 Sep 2022)

References

nvd.nist.gov/vuln/detail/CVE-2020-0688

Questions

Is CVE-2020-0688 being exploited?

Yes. CISA added CVE-2020-0688 to the Known Exploited Vulnerabilities catalog on 3 Nov 2021, which means there is reliable evidence of exploitation in the wild.

Is CVE-2020-0688 used in ransomware attacks?

Yes, CISA lists it as known to be used in ransomware campaigns.

How do I fix CVE-2020-0688?

Apply updates per vendor instructions. Check Microsoft's advisory for the fixed versions, and if you can't patch quickly, restrict access to the affected Exchange Server and watch it for signs of compromise.

Sources: CISA KEV (exploitation, ransomware use, required action, due date), the CVE record (publication date, CVSS, CNA), NVD and FIRST EPSS (live score). More: all KEV additions in November 2021 · Microsoft scorecard · act-now radar.

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