Home / Vulnerabilities / CVE-2021-26857
HIGH SEVERITY Ransomware Linked
CVE-2021-26857 Microsoft · Exchange Server

Microsoft Exchange Server Remote Code Execution Vulnerability

Critical Threat Advisory: This vulnerability is documented in active Ransomware campaigns. Immediate remediation required.

Technical Severity

CVSS v3.1 Metrics

HIGH
7.8 / 10
Minimal Risk Critical
Vector Specification
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C
Exploitation Likelihood

EPSS Prediction

34.54 %
Predictive Probability
Percentile Rank
96.9 th

Documented as more likely to be exploited than 96.9% of known CVEs.

Detection Date

Nov 03, 2021

Remediation Due

May 03, 2022

CISA Catalog Active

Threat Analysis

Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution. This vulnerability is part of the ProxyLogon exploit chain.

Remediation Directive

Apply updates per vendor instructions.

External Intelligence

CISA

CISA Advisory

https://www.cisa.gov/news-events/directives/ed-21-02-mitigate-microsoft-exchange-premises-product-vulnerabilities)