CVE-2023-23397: Microsoft Office Outlook Privilege Escalation Vulnerability
- Is it exploited?
Yes. CISA added it to the Known Exploited Vulnerabilities catalog on , the same day the CVE record was published.
- How likely is exploitation in the next 30 days?
- 97.2%
EPSS score, percentile 99.9 of all scored records
- How severe?
- 9.8 Critical
CVSS v3.1 base score, given by the CNA
- What should I do?
CISA deadline . Apply updates per vendor instructions.
- Which versions are affected?
Affected
- 16.0.1
- from 16.0.0.0 to before 16.0.5387.1000
- 16.0.1
- 19.0.0
- from 15.0.0.0 to before 15.0.5537.1000
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of ; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of ; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
What to do
Required action, set by CISA
Apply updates per vendor instructions.
CISA due date for this action: .
Advisories and patches
Linked from CISA's catalog entry
- https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2023-23397
- https://msrc.microsoft.com/blog/2023/03/microsoft-mitigates-outlook-elevation-of-privilege-vulnerability/
- https://nvd.nist.gov/vuln/detail/CVE-2023-23397
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | 16.0.1 |
| Status | Versions |
|---|---|
| Affected | from 16.0.0.0 to before 16.0.5387.1000 |
| Status | Versions |
|---|---|
| Affected | 16.0.1 |
| Status | Versions |
|---|---|
| Affected | 19.0.0 |
| Status | Versions |
|---|---|
| Affected | from 15.0.0.0 to before 15.0.5537.1000 |
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
About this vulnerability
Microsoft Office Outlook contains a privilege escalation vulnerability that allows for a NTLM Relay attack against another service to authenticate as the user.
Summary: CISA's KEV catalog, as of .
- CISA added CVE-2023-23397 to its Known Exploited Vulnerabilities (KEV) catalog on 14 Mar 2023.
- CISA's ransomware flag for this entry is "Unknown": no evidence of ransomware use in the catalog, which is not proof of none.
- The due date CISA sets for the required action is 4 Apr 2023.
- The CVE record was published on 14 Mar 2023, the same day it was added to KEV.
- The CVE record carries a CVSS v3.1 base score of 9.8 (Critical), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 97.2% (percentile 99.9), 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 ; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of ; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of . About the data.
Description
Microsoft Outlook Elevation of Privilege Vulnerability
Microsoft Outlook Elevation of Privilege Vulnerability
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
Weakness
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.
Timeline
| Date | Event |
|---|---|
| CVE record published | |
| Added to CISA KEV | |
| CISA due date for the required action | |
| CVE record last updated |
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