Credential theft via untrusted reminder UNC path
Published Mar 14, 2023 · Updated Oct 21, 2025
Credential exposure in Microsoft Outlook for Windows allows remote attackers to leak Net-NTLMv2 hashes through crafted messages. Outlook trusts the PidLidReminderFileParameter extended MAPI property and fetches a reminder sound from an attacker-controlled UNC path over SMB. No user interaction is required when Outlook is open and the reminder fires; the captured hash supports offline cracking or relay authentication.
Summary
What happened
Credential exposure in Microsoft Outlook for Windows allows remote attackers to leak Net-NTLMv2 hashes through crafted messages. Outlook trusts the PidLidReminderFileParameter extended MAPI property and fetches a reminder sound from an attacker-controlled UNC path over SMB. No user interaction is required when Outlook is open and the reminder fires; the captured hash supports offline cracking or relay authentication.
The record
- CVE
- CVE-2023-23397
- Published
- Mar 14, 2023
- Updated
- Oct 21, 2025
- Vendor
- Microsoft
- Product
- Microsoft Office 2019
- Classifications
- CWE-294, CWE-20, T1187
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 1, 2022Exploitation reportedForest Blizzard exploitation of Outlook credential theft
- Mar 14, 2023Exploitation reportedCISA Known Exploited Vulnerabilities listing
- Mar 14, 2023CVE publishedPublication date reported by the CVE source.
- Oct 21, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=19.0.0 <https://aka.ms/OfficeSecurityReleases
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
Public exploit references
- CVE-2023-23397 POC PowerShellproof of concept · unverified
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Reported exploitation
- Forest Blizzard exploitation of Outlook credential theftthreat actor
- CISA Known Exploited Vulnerabilities listingknown exploited catalog
Technologies
Your stack
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Your stack
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