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CVE-2021-34523: Microsoft Exchange Server Privilege Escalation Vulnerability

CVE-2021-34523 is rated critical with a CVSS v3.1 base score of 9.8 and affects Microsoft Exchange Server. Per its scoring, it can be exploited over the network, without authentication, without any user interaction. The scored impact on confidentiality, integrity and availability is the highest available. CISA added it to its Known Exploited Vulnerabilities catalog on 2021-11-03, which means exploitation in the wild has been observed.

Vulnerability description

Microsoft Exchange Server Elevation of Privilege Vulnerability

Severity breakdown

CVSS v3.1 9.8: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

  • Attack vector: Network. Exploitable remotely over the network, with no need for local or physical access.
  • Attack complexity: Low. No special conditions; the attack can be repeated reliably.
  • Privileges required: None. No account or prior access is needed.
  • User interaction: None. No action from any user is needed.
  • Scope: Unchanged. Impact stays within the vulnerable component.
  • Confidentiality impact: High. Total loss of confidentiality; sensitive data can be fully disclosed.
  • Integrity impact: High. Total loss of integrity; data or system state can be fully modified.
  • Availability impact: High. Total loss of availability; the component can be shut down.

Affected products

  • Microsoft Exchange Server: 2013 cumulative_update_23; 2016 cumulative_update_19; 2016 cumulative_update_20; 2019 cumulative_update_8; 2019 cumulative_update_9

References