Security Notice bypass via hyperlink TOCTOU race
Published Jul 11, 2023 · Updated Oct 21, 2025
A TOCTOU race in Microsoft Outlook allows remote attackers to bypass the Security Notice after clicking a crafted email link. Outlook's hyperlink handling checks a target and later opens it without ensuring the checked resource remains unchanged. User interaction is required; a successful race suppresses the warning before untrusted linked content opens.
Summary
What happened
A TOCTOU race in Microsoft Outlook allows remote attackers to bypass the Security Notice after clicking a crafted email link. Outlook's hyperlink handling checks a target and later opens it without ensuring the checked resource remains unchanged. User interaction is required; a successful race suppresses the warning before untrusted linked content opens.
The record
- CVE
- CVE-2023-35311
- Published
- Jul 11, 2023
- Updated
- Oct 21, 2025
- Vendor
- Microsoft
- Product
- Microsoft Office 2019
- Classifications
- CWE-367, T1211
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 11, 2023Exploitation reportedCISA Known Exploited Vulnerabilities Catalog entry
- Jul 11, 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?
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
No public exploit references are available in this record.
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Reported exploitation
- CISA Known Exploited Vulnerabilities Catalog entryknown exploited catalog
Technologies
Your stack
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Your stack
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