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Fencer Intel
high 7.8

CVE-2026-55009 json

Microsoft Exchange Server Elevation of Privilege Vulnerability

published 3mo ago modified 8d ago also EUVD-2026-44027

cvss
7.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
2.5%
EPSS 2.5% chance of exploitation in 30 days, percentile 84%
public exploits
0
none known

Summary

Deserialization of untrusted data in Microsoft Exchange Server allows an authorized attacker to elevate privileges locally.

Patch / fix

  • Microsoft Microsoft Exchange Server 2016 Cumulative Update 23 15.01.2507.071
  • Microsoft Microsoft Exchange Server 2019 Cumulative Update 14 15.02.1544.043
  • Microsoft Microsoft Exchange Server 2019 Cumulative Update 15 15.02.1748.048
  • Microsoft Microsoft Exchange Server Subscription Edition RTM 15.02.2562.045

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CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
3mo ago

Exploit prediction

2.51% chance of exploitation in the next 30 days, higher than 84% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
CNA 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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-502 Deserialization of Untrusted Data
Technology feeds

References

Sources

Fencer Intel 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.