CVE-2021-26858: listed in the CISA KEV catalog

CVE-2021-26858 · CVSS 7.8 HIGH · EPSS 90% · KEV 2021-11-03

Microsoft Exchange Server Remote Code Execution Vulnerability

Is CVE-2021-26858 exploited?

• Listed in the CISA KEV catalog on 2021-11-03.
• Federal remediation due 2022-05-03.
• Past that date by 1565 days.
• Used in ransomware campaigns.
• EPSS puts exploitation in the next 30 days at 90%.
• Public exploit code: none found in monitored sources.

Which products and versions are affected?

No affected package list recorded here yet.

Is there a patch?

No patch identifier recorded here yet.

What PlainSec published about CVE-2021-26858

• ShadowPad Espionage Campaign Targets Exchange and IIS Servers (2026-05-05)

Primary sources

• NVD record
• CISA KEV catalog

What this record does not say

• No affected package data.
• No patch identifier.

KEV and EPSS are re-checked daily. Record last updated 2026-08-11.