CVE-2026-55009: CWE-502: Deserialization of Untrusted Data in Microsoft Microsoft Exchange Server 2016 Cumulative Update 23
Deserialization of untrusted data in Microsoft Exchange Server allows an authorized attacker to elevate privileges locally.
AI Analysis
Technical Summary
This vulnerability (CVE-2026-55009) in Microsoft Exchange Server 2016 Cumulative Update 23 arises from improper deserialization of untrusted data, classified under CWE-502. It enables an attacker with local authorized access to escalate privileges on the affected system. The CVSS 3.1 base score is 7.8, reflecting high impact on confidentiality, integrity, and availability. Microsoft has released an official fix to address this issue.
Potential Impact
An authorized local attacker can exploit this vulnerability to elevate their privileges, potentially gaining higher-level access than intended. This can lead to full compromise of the affected Exchange Server instance, impacting confidentiality, integrity, and availability of the system and its data.
Mitigation Recommendations
An official fix is available from Microsoft. Administrators should apply the security update provided in the Microsoft advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55009 to remediate this vulnerability.
CVE-2026-55009: CWE-502: Deserialization of Untrusted Data in Microsoft Microsoft Exchange Server 2016 Cumulative Update 23
Description
Deserialization of untrusted data in Microsoft Exchange Server allows an authorized attacker to elevate privileges locally.
CVSS v3.1
Score 7.8high
Affected software
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability (CVE-2026-55009) in Microsoft Exchange Server 2016 Cumulative Update 23 arises from improper deserialization of untrusted data, classified under CWE-502. It enables an attacker with local authorized access to escalate privileges on the affected system. The CVSS 3.1 base score is 7.8, reflecting high impact on confidentiality, integrity, and availability. Microsoft has released an official fix to address this issue.
Potential Impact
An authorized local attacker can exploit this vulnerability to elevate their privileges, potentially gaining higher-level access than intended. This can lead to full compromise of the affected Exchange Server instance, impacting confidentiality, integrity, and availability of the system and its data.
Mitigation Recommendations
An official fix is available from Microsoft. Administrators should apply the security update provided in the Microsoft advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55009 to remediate this vulnerability.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- microsoft
- Date Reserved
- 2026-06-16T14:12:44.283Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- official-fix
- Vendor Advisory Urls
- [{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55009","vendor":"Microsoft"}]
Threat ID: 6a566f8068715ace43e6bf6d
Added to database: 07/14/2026, 17:18:56 UTC
Last enriched: 07/14/2026, 17:48:54 UTC
Last updated: 07/15/2026, 04:18:39 UTC
Views: 3
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