CVE-2021-33766

CVE-2021-33766 is a high-severity (CVSS 7.3) vulnerability in Microsoft Exchange Server. CISA added it to the Known Exploited Vulnerabilities catalog on January 18, 2022, which means exploitation in the wild has been confirmed; US federal agencies had to remediate it by February 1, 2022. CISA does not currently list it as used in ransomware campaigns. Microsoft has 390 vulnerabilities in the KEV catalog, 117 of them linked to ransomware.

Microsoft Exchange Server Information Disclosure Vulnerability

CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-33766
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-33766
• https://www.zerodayinitiative.com/advisories/ZDI-21-798/
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-33766