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Exploited vulnerability · CISA KEV

Is CVE-2023-35311 exploited? Yes: in CISA KEV since 11 Jul 2023

Gociux · Microsoft Outlook · data: CISA KEV, CVE record, FIRST EPSS

Yes. CVE-2023-35311, Microsoft Outlook Security Feature Bypass Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 11 Jul 2023, the day it was published. It affects Microsoft Outlook. If you run it, CISA's required action is: Apply updates per vendor instructions or discontinue use of the product if updates are unavailable.

exploitedYesCISA KEV · 11 Jul 2023
ransomwareNot knownno confirmed use
EPSStop 5%very likely to be exploited
severity8.8CVSS 3.1 · high
US federal due1 Aug 2023BOD 22-01 deadline

What it is

Microsoft Outlook contains a security feature bypass vulnerability that allows an attacker to bypass the Microsoft Outlook Security Notice prompt.

VendorMicrosoft (391 exploited CVEs in KEV)
ProductOutlook
VulnerabilityMicrosoft Outlook Security Feature Bypass Vulnerability
WeaknessCWE-367
Published11 Jul 2023
Added to KEV11 Jul 2023
Reported by (CNA)microsoft

What to do

  1. Check whether you run it. Look for Outlook in your asset inventory, including appliances and cloud images. Stack check lists every exploited Microsoft CVE at once.
  2. Apply the fix. Apply updates per vendor instructions or discontinue use of the product if updates are unavailable.
  3. If you can't patch today, take the affected service off the internet or restrict who can reach it, and check its logs for signs of compromise since 11 Jul 2023.
  4. Get told next time. Email alerts when CISA adds a CVE for Microsoft.

References

Questions

Is CVE-2023-35311 being exploited?

Yes. CISA added CVE-2023-35311 to the Known Exploited Vulnerabilities catalog on 11 Jul 2023, which means there is reliable evidence of exploitation in the wild.

Is CVE-2023-35311 used in ransomware attacks?

CISA does not list known ransomware use for it. That can change, and exploitation alone is reason to fix it first.

How do I fix CVE-2023-35311?

Apply updates per vendor instructions or discontinue use of the product if updates are unavailable. Check Microsoft's advisory for the fixed versions, and if you can't patch quickly, restrict access to the affected Outlook and watch it for signs of compromise.

Sources: CISA KEV (exploitation, ransomware use, required action, due date), the CVE record (publication date, CVSS, CNA), NVD and FIRST EPSS (live score). More: all KEV additions in July 2023 · Microsoft scorecard · act-now radar.

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