CVE-2026-55009

Status: AnalyzedHigh (7.8)—

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

CVSS

Version: 3.1
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Base score: 7.8

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days: 2.51%
Percentile among all scored CVEs: 84
Score date: 10/3/2026

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

🎯 ATT&CK techniques

How this vulnerability is exploited and what the attacker gains, in MITRE ATT&CK terms.

ExploitationT1068 Exploitation for Privilege Escalationprivilege escalation95 %
Primary impactT1059 Command and Scripting Interpreterexecution85 %

AV:L sin UI:N con PR:L indica escalada local. CWE-502 (deserialización) en Exchange permite ejecución de código con privilegios elevados tras autenticación inicial.

Inferred by our analysis agent from the official description, CVSS vector and CWE, and checked by a supervisor. May contain errors.

🛡️ ATT&CK mitigations that cover these techniques

Execution Prevention Threat Intelligence Program Restrict Web-Based Content Privileged Account Management Limit Software Installation Behavior Prevention on Endpoint

Affected technologies (2)

Microsoft — Exchange Server Microsoft — Exchange Server Subscription Edition

CWEs

CWE-502

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55009

Raw JSON (NVD)

Show

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