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) affects Microsoft Exchange Server 2016 Cumulative Update 23 (version 15.01.0.0). It involves CWE-502: Deserialization of Untrusted Data, where an attacker with local authorized access can exploit improper deserialization to elevate privileges. The CVSS 3.1 base score is 7.8, indicating high severity, with impact on confidentiality, integrity, and availability. Microsoft has published an official fix for this issue.
Potential Impact
An authorized local attacker can leverage this vulnerability to elevate their privileges on the affected Microsoft Exchange Server 2016 system, potentially gaining higher-level access and control. The impact affects confidentiality, integrity, and availability of the system as indicated by the CVSS vector.
Mitigation Recommendations
Microsoft has released an official fix for this vulnerability. Users of Microsoft Exchange Server 2016 Cumulative Update 23 (version 15.01.0.0) should apply the vendor-provided patch as detailed in the Microsoft advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55009 to remediate this issue.
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) affects Microsoft Exchange Server 2016 Cumulative Update 23 (version 15.01.0.0). It involves CWE-502: Deserialization of Untrusted Data, where an attacker with local authorized access can exploit improper deserialization to elevate privileges. The CVSS 3.1 base score is 7.8, indicating high severity, with impact on confidentiality, integrity, and availability. Microsoft has published an official fix for this issue.
Potential Impact
An authorized local attacker can leverage this vulnerability to elevate their privileges on the affected Microsoft Exchange Server 2016 system, potentially gaining higher-level access and control. The impact affects confidentiality, integrity, and availability of the system as indicated by the CVSS vector.
Mitigation Recommendations
Microsoft has released an official fix for this vulnerability. Users of Microsoft Exchange Server 2016 Cumulative Update 23 (version 15.01.0.0) should apply the vendor-provided patch as detailed in the Microsoft advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55009 to remediate this issue.
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: 08/13/2026, 15:28:08 UTC
Last updated: 08/26/2026, 22:52:11 UTC
Views: 49
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