Vulnerability in Microsoft Exchange Server 2013 Cumulative Update 21
CVE-2021-26858
Microsoft Exchange Server Remote Code Execution Vulnerability
EPSS: 0.732 (98.8th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.8 (High). Vector: 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.
Affected products
- Microsoft Exchange Server 2013 Cumulative Update 21 — versions 15.00.0
- Microsoft Exchange Server 2013 Cumulative Update 22 — versions 15.00.0
- Microsoft Exchange Server 2013 Cumulative Update 23 — versions 15.00.0
- Microsoft Exchange Server 2016 Cumulative Update 10 — versions 15.01.0
- Microsoft Exchange Server 2016 Cumulative Update 11 — versions 15.01.0
- Microsoft Exchange Server 2016 Cumulative Update 12 — versions 15.01.0
- Microsoft Exchange Server 2016 Cumulative Update 13 — versions 15.01.0
- Microsoft Exchange Server 2016 Cumulative Update 14 — versions 15.01.0
- Microsoft Exchange Server 2016 Cumulative Update 15 — versions 15.01.0
- Microsoft Exchange Server 2016 Cumulative Update 16 — versions 15.01.0
CISA KEV (Known Exploited Vulnerabilities)
This CVE is on the CISA KEV catalog, added on . CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.
BOD 22-01 due date: .
Required action: Apply updates per vendor instructions.
Known ransomware campaign use: yes.
Public proof-of-concept exploits
References
- portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26858 (x_refsource_MISC)
Frequently asked questions
- What is CVE-2021-26858?
- CVE-2021-26858 is a high-severity vulnerability in Microsoft Exchange Server 2013 Cumulative Update 21. CVSS score: 7.8/10. Published 2021-03-02.
- How severe is CVE-2021-26858?
- High severity. CVSS v3 base score is 7.8 out of 10.
- Is CVE-2021-26858 known to be exploited?
- Yes. CVE-2021-26858 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03), indicating it is being actively exploited. 60 public proof-of-concept repositories are indexed.