What it is
CVE-2023-35311 is an unauthenticated Microsoft Outlook Security Feature Bypass Vulnerability.
Vulnerability report
Exploited in the wild
Confirmed confidence
In CISA KEV
CVE-2023-35311
Microsoft Outlook Security Feature Bypass Vulnerability
Microsoft / Microsoft 365 Apps for Enterprise · affected before https://aka.ms/OfficeSecurityReleases
- Severity
- CVSS 8.8 · High
- Confidence
- Confirmed
- Exploit status
- Exploited in the wild
- EPSS
- 15.5%
- First observed
- —
- Last observed
- —
Decision summary
What security teams need to know first
Direct answers before the deeper technical record.
Is it exploited?
Yes. KEV Intelligence tracks this CVE as a known exploited vulnerability. Confidence is confirmed.
Who is affected?
Microsoft / Microsoft 365 Apps for Enterprise affected before https://aka.ms/officesecurityreleases.
What should we do?
Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.
Overview
Microsoft Outlook Security Feature Bypass Vulnerability
Microsoft Outlook Security Feature Bypass Vulnerability
Vendor
Product
Affected
Status
Microsoft
Microsoft 365 Apps for Enterprise
Before https://aka.ms/OfficeSecurityReleases
Affected
Microsoft
Microsoft Office LTSC 2021
Before https://aka.ms/OfficeSecurityReleases
Affected
Microsoft
Microsoft Office 2019
Before https://aka.ms/OfficeSecurityReleases
Affected
Microsoft
Microsoft Outlook 2016
Before 16.0.5404.1000
Affected
Microsoft
Microsoft Outlook 2013
Before 15.0.5571.1000
Affected
Microsoft
Microsoft Outlook 2013 Service Pack 1
Before 15.0.5571.1000
Affected
- Published
- 11 Jul 2023
- Exploitation Reported
- 11 Jul 2023
- Attack vector
- Remote
- Complexity
- Low
- Privileges
- None
- User interaction
- Required
Tags
microsoft
cisa
nessus_scanner
CVE References
- CVE Record CVE.org · CVE Record https://www.cve.org/CVERecord?id=CVE-2023-35311
- Microsoft Outlook Security Feature Bypass Vulnerability msrc.microsoft.com · Vendor Advisory https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-35311
Exploitation evidence
Why KEV Intelligence marks this CVE as exploited
Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.
Exploited in the wild
CISA
Independent exploitation attestation added to the KEV Intelligence record.
Known exploited vulnerability sources
Per-source evidence links for KEV attestations are available through the KEV Intelligence Pro API.
Learn about Pro API access| Source | Added |
|---|---|
| CISA First | 2023-07-11 00:00 UTC |
Detection
Operational artifacts and observed signals
Make the evidence actionable in scanner, SOC, and edge-control workflows.
Observed signals
- Request targets
- 0
- User-Agents
- 0
Raw values available in Pro and Enterprise.
Scanner coverage
Nessus template detected 02 Jun 2025.
View Nessus template (opens in new tab)Virtual patch status
No KEV Intelligence virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.
Learn about virtual patches →Scanner Artifacts
Scanner and exploit-framework references linked to this CVE.
| Scanner | Reference | Detected |
|---|---|---|
| Nessus | https://www.tenable.com/plugins/nessus/178203 | 02 Jun 2025 |
Risk and context
Severity, weaknesses, and research context
CVSS v3.1
8.8
High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C
EPSS
15.5%
Timeline
From disclosure to observed exploitation
-
Nessus plugin available
Scanner coverage available
-
CVE published
Vulnerability disclosed publicly
-
Added to CISA KEV
Listed in the CISA Known Exploited Vulnerabilities catalog
-
CVE ID reserved
Identifier reserved by the CNA
Pro API
Automate this intelligence
Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.
- Evidence confidence and provenance
- First-party sensor telemetry
- PoC and scanner references
- Affected versions and enrichment
- Automation-ready JSON delivery
GET /api/v2/pro/kevs/CVE-2023-35311
Free JSON includes basic KEV fields{
"cve_id": "CVE-2023-35311",
"confidence": "Confirmed",
"cvss_score": 8.8,
"cvss_estimated": false,
"epss_score": 0.15522,
"exploit_status": {
"exploited_in_the_wild": true,
"active_exploitation_observed": false
},
"sensor_telemetry": { "attempts": 0, "sensors": 0 }
}Early warning alerts
Get alerts on high-impact exploitation
Receive curator-selected alerts when exploitation activity warrants attention. Each alert includes the evidence and context needed to decide what requires attention now.