CVEvulnerability
CVE-2021-26858
CISA Known Exploited Vulnerability
Microsoft Exchange Server Remote Code Execution Vulnerability — Microsoft Exchange Server
Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution. This vulnerability is part of the ProxyLogon exploit chain.
- Added to KEV
- 2021-11-03
- Remediation due
- 2022-05-03
- Ransomware use
- Known
- Required action
- Apply updates per vendor instructions.
- 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-2021-26858
- Status
- Analyzed
- Published
- 2021-03-03
- Last modified
- 2026-10-01
- Assigner
- [email protected]
- CVSS 3.1 ([email protected])
- 7.8 HIGH — CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- CVSS 3.1 ([email protected])
- 7.8 HIGH — CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- CVSS 2.0 ([email protected])
- 6.8 MEDIUM — AV:N/AC:M/Au:N/C:P/I:P/A:P
Description
Microsoft Exchange Server Remote Code Execution Vulnerability
Affected configurations
• microsoft exchange server 2013
• microsoft exchange server 2016
• microsoft exchange server 2019
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26858 Patch, Vendor Advisory
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26858 Patch, Vendor Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26858 US Government Resource