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Fencer Vulns
medium 6.5

CVE-2026-21527 json

Microsoft Exchange Server Spoofing Vulnerability

published 2026-02-10 8 mo ago modified 2026-08-19 2 mo ago also EUVD-2026-7340

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
8.1%
EPSS 8.1% chance of exploitation in 30 days, percentile 94%
public exploits
0
none known

Summary

User interface (ui) misrepresentation of critical information in Microsoft Exchange Server allows an unauthorized attacker to perform spoofing over a network.

Patch / fix

  • Microsoft Microsoft Exchange Server 2016 Cumulative Update 23 15.01.2507.066
  • Microsoft Microsoft Exchange Server 2019 Cumulative Update 14 15.02.1544.039
  • Microsoft Microsoft Exchange Server 2019 Cumulative Update 15 15.02.1748.043
  • Microsoft Microsoft Exchange Server Subscription Edition RTM 15.02.2562.037

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
8 mo ago

Exploit prediction

8.14% chance of exploitation in the next 30 days, higher than 94% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N/E:U/RL:O/RC:C
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Affected products

  • Microsoft Microsoft Exchange Server 2016 Cumulative Update 23
  • Microsoft Microsoft Exchange Server 2019 Cumulative Update 14
  • Microsoft Microsoft Exchange Server 2019 Cumulative Update 15
  • Microsoft Microsoft Exchange Server Subscription Edition RTM

Classification

Weakness
  • CWE-451 User Interface (UI) Misrepresentation of Critical Information
  • CWE-345 Insufficient Verification of Data Authenticity
  • CWE-1286 Improper Validation of Syntactic Correctness of Input
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.