CVE-2023-35311
HighExploitedPublic exploitMicrosoft Outlook Security Feature Bypass Vulnerability
Published Jul 11, 2023 · Updated Oct 8, 2026
Key Facts
Patch immediately- CVE-2023-35311 is a high-severity vulnerability (CVSS 7.5 v3.1) affecting 365 Apps (Microsoft), Office (Microsoft), Office 2019 (Microsoft) and 8 more products.
- It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Jul 11, 2023. Public exploit code is available.
- EPSS estimates a 16% probability of exploitation in the next 30 days.
- Fixed versions are available, including Microsoft 365 Apps for Enterprise https://aka.ms/OfficeSecurityReleases, Office 2019 https://aka.ms/OfficeSecurityReleases, Microsoft Office LTSC 2021 https://aka.ms/OfficeSecurityReleases.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
7.5
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
EPSS (30-day exploit likelihood)
16%
Higher than 96.7% of all scored CVEs
Exploited in the wild
Yes
4 catalog listings
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2023-35311 brief as a PDF
Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.
Description
Microsoft Outlook Security Feature Bypass Vulnerability
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CISA KEV | Jul 11, 2023 | Aug 1, 2023 | Not reported |
| Industry KEV feed | Jul 11, 2023 | Aug 1, 2023 | Not reported |
| CIRCL KEV | Jul 11, 2023 | Aug 1, 2023 | Not reported |
| ENISA EUVD | Jul 11, 2023 | n/a | Not reported |
Required action: Apply updates per vendor instructions or discontinue use of the product if updates are unavailable.
Affected Products
22 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| 365 AppsMicrosoft | See advisory | n/a |
| OfficeMicrosoft | 2019 | n/a |
| Office 2019Microsoft | >= 19.0.0 | https://aka.ms/OfficeSecurityReleases |
| Office 2021Microsoft | See advisory | n/a |
| Office Long Term Servicing ChannelMicrosoft | 2021 | n/a |
Patched Releases
Microsoft 365 Apps for Enterprise
https://aka.ms/OfficeSecurityReleases
Office 2019
https://aka.ms/OfficeSecurityReleases
Microsoft Office LTSC 2021
https://aka.ms/OfficeSecurityReleases
Outlook
15.0.5571.1000, 16.0.5404.1000
Microsoft Outlook 2013
15.0.5571.1000
Microsoft Outlook 2013 Service Pack 1
15.0.5571.1000
Microsoft Outlook 2016
16.0.5404.1000
Timeline
Publicly disclosed
Jul 11, 2023
Added to CISA KEV
Jul 11, 2023
Added to Industry KEV feed
Jul 11, 2023
Added to CIRCL KEV
Jul 11, 2023
Added to ENISA EUVD
Jul 11, 2023
Last updated
Oct 8, 2026
Weakness Type
- CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition
References
FAQ
Common Questions.
Microsoft Outlook Security Feature Bypass Vulnerability
Affected: 365 Apps (Microsoft); Office (Microsoft) versions 2019; Office 2019 (Microsoft) versions >= 19.0.0, among others. The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Jul 11, 2023.
Yes. It was added on Jul 11, 2023 with a federal remediation due date of Aug 1, 2023.
Public exploit code is available.
Fixed versions are available, including Microsoft 365 Apps for Enterprise https://aka.ms/OfficeSecurityReleases, Office 2019 https://aka.ms/OfficeSecurityReleases, Microsoft Office LTSC 2021 https://aka.ms/OfficeSecurityReleases.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
Is CVE-2023-35311 Running On Your Attack Surface?
Brandefense maps vulnerabilities like this one to your internet-facing assets and tells you exactly where to patch.
Request A Demo