CVE-2023-23397: Microsoft Office Outlook Privilege Escalation Vulnerability
Affects Microsoft OfficeSource CISA KEV
Exploited in the wild · KEV due 4 Apr 2023 · 97% EPSS : apply the vendor's fix or mitigations to Microsoft Office now.
Data as of 10/24/2026, 22:15:59 UTC
- Exploitation
Actively exploited – in CISA KEV since 03/14/2023
- KEV deadline
- 04/04/2023 US federal agencies must patch by this date; a sensible deadline for everyone else.
- EPSS
- 97.1% chance of exploitation in 30 days – higher than 99% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:CWhat to do
CISA required action
Apply updates per vendor instructions.
Description
Microsoft Office Outlook contains a privilege escalation vulnerability that allows for a NTLM Relay attack against another service to authenticate as the user.
Weaknesses
- CWE-294Authentication Bypass by Capture-replay (opens in a new tab)
Base weaknessLikelihood of exploit: HighOWASP Top 10 A07:2025: Authentication Failures (opens in a new tab)
A capture-replay flaw exists when the design of the product makes it possible for a malicious user to sniff network traffic and bypass authentication by replaying it to the server in question to the same effect as the original message (or with minor changes).
References
- msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2023-23397, (opens in a new tab)
- msrc.microsoft.com/blog/2023/03/microsoft-mitigates-outlook-elevation-of-privilege-vulnerability/, (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2023-23397 (opens in a new tab)
- cisa.gov/known-exploited-vulnerabilities-catalog?search=CVE-2023-23397 (opens in a new tab)