CVE-2026-56191: CWE-287: Improper Authentication in Microsoft Microsoft Exchange Online
Improper authentication in Microsoft Exchange Online allows an unauthorized attacker to perform tampering over a network.
AI Analysis
Technical Summary
This vulnerability, identified as CWE-287 (Improper Authentication), affects Microsoft Exchange Online and enables an attacker without privileges or user interaction to tamper with the service over a network. The CVSS 3.1 vector indicates network attack vector, low attack complexity, no privileges required, no user interaction, scope changed, and high impact on confidentiality, integrity, and availability. Microsoft has published an official fix for this vulnerability.
Potential Impact
Successful exploitation allows an unauthorized attacker to bypass authentication controls and perform tampering actions within Microsoft Exchange Online, potentially compromising confidentiality, integrity, and availability of the service and its data.
Mitigation Recommendations
An official fix is available from Microsoft. Users and administrators should apply the security update provided in the Microsoft advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56191 to remediate this vulnerability.
CVE-2026-56191: CWE-287: Improper Authentication in Microsoft Microsoft Exchange Online
Description
Improper authentication in Microsoft Exchange Online allows an unauthorized attacker to perform tampering over a network.
CVSS v3.1
Score 10.0critical
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability, identified as CWE-287 (Improper Authentication), affects Microsoft Exchange Online and enables an attacker without privileges or user interaction to tamper with the service over a network. The CVSS 3.1 vector indicates network attack vector, low attack complexity, no privileges required, no user interaction, scope changed, and high impact on confidentiality, integrity, and availability. Microsoft has published an official fix for this vulnerability.
Potential Impact
Successful exploitation allows an unauthorized attacker to bypass authentication controls and perform tampering actions within Microsoft Exchange Online, potentially compromising confidentiality, integrity, and availability of the service and its data.
Mitigation Recommendations
An official fix is available from Microsoft. Users and administrators should apply the security update provided in the Microsoft advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56191 to remediate this vulnerability.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- microsoft
- Date Reserved
- 2026-06-19T13:54:04.006Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- official-fix
- Vendor Advisory Urls
- [{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56191","vendor":"Microsoft"}]
Threat ID: 6a62b3ff9c2644c7f8000d5a
Added to database: 07/24/2026, 00:38:23 UTC
Last enriched: 08/15/2026, 13:24:05 UTC
Last updated: 09/06/2026, 20:06:52 UTC
Views: 393
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