CVE-2021-26857—Microsoft Exchange Server Remote Code Execution Vulnerability

Vulnerability Name

Microsoft Exchange Server Remote Code Execution Vulnerability

Description

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

Known To Be Used in Ransomware Campaigns?

Ransomware Status:

KNOWN

Action

Apply updates per vendor instructions.

Additional Notes

• Reference CISA's ED 21-02 (https://www.cisa.gov/news-events/directives/ed-21-02-mitigate-microsoft-exchange-premises-product-vulnerabilities) for further guidance and requirements. Note: The due date for addressing this vulnerability aligns with the requirements outlined in ED 21-02. https://nvd.nist.gov/vuln/detail/CVE-2021-26857

Related News Articles

• Hackers Target Over 70 Microsoft Exchange Servers to Steal Credentials via KeyloggersJune 24, 2025
• US indicts Black Kingdom ransomware admin for Microsoft Exchange attacksMay 2, 2025
• Chinese Hackers Use GHOSTSPIDER Malware to Hack Telecoms Across 12+ CountriesNovember 26, 2024
• Salt Typhoon hackers backdoor telcos with new GhostSpider malwareNovember 25, 2024
• AT&T, Verizon reportedly hacked to target US govt wiretapping platformOctober 7, 2024

Related Weaknesses

• CWE-502