CVE-2020-0688: Microsoft Exchange Server Validation Key Remote Code Execution Vulnerability
- Is it exploited?
Yes. CISA added it to the Known Exploited Vulnerabilities catalog on 3 Nov 2021, 631 days after the CVE record was published.
- How likely is exploitation in the next 30 days?
- 100%
EPSS score, percentile 100 of all scored records
- How severe?
- 8.8 High
CVSS v3.1 base score, from CISA's enrichment of the record
- What should I do?
Required action (CISA), due 3 May 2022: Apply updates per vendor instructions.
The CVE record links no vendor advisory, patch or mitigation.
- Which versions are affected?
Affected: Cumulative Update 23; unspecified; unspecified; unspecified; unspecified; unspecified
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
What to do
Required action, set by CISA
Apply updates per vendor instructions.
CISA due date for this action: 3 May 2022.
Advisories and patches
The CVE record links no vendor advisory, patch or mitigation.
Linked from CISA's catalog entry
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | Cumulative Update 23 |
| Status | Versions |
|---|---|
| Affected | unspecified |
| Status | Versions |
|---|---|
| Affected | unspecified |
| Status | Versions |
|---|---|
| Affected | unspecified |
| Status | Versions |
|---|---|
| Affected | unspecified |
| Status | Versions |
|---|---|
| Affected | unspecified |
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
About this vulnerability
Microsoft Exchange Server Validation Key fails to properly create unique keys at install time, allowing for remote code execution.
Summary: CISA's KEV catalog, as of 28 Oct 2026.
- CISA added CVE-2020-0688 to its Known Exploited Vulnerabilities (KEV) catalog on 3 Nov 2021.
- CISA marks it as known to be used in ransomware campaigns.
- The due date CISA sets for the required action is 3 May 2022.
- The CVE record was published on 11 Feb 2020, 631 days before it was added to KEV.
- The CVE record carries a CVSS v3.1 base score of 8.8 (High), taken from CISA's enrichment of the record.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 100% (percentile 100), as of 28 Oct 2026.
- CISA's SSVC assessment in the CVE record: exploitation active, automatable no, technical impact total.
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026. About the data.
Description
A remote code execution vulnerability exists in Microsoft Exchange software when the software fails to properly handle objects in memory, aka 'Microsoft Exchange Memory Corruption Vulnerability'.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
Weakness
- CWE-287: Improper Authentication
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.
Timeline
| Date | Event |
|---|---|
| 11 Feb 2020 | CVE record published |
| 3 Nov 2021 | Added to CISA KEV |
| 3 May 2022 | CISA due date for the required action |
| 21 Oct 2025 | CVE record last updated |
References
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