EUVD-2026-56723
GHSA-mvrg-82pf-2wp2
Severity by source
AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
Network-reachable with no attacker privileges; user action triggers credential exposure; impact confined to limited confidentiality with no integrity or availability effect.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
3DescriptionCVE.org
Insufficiently protected credentials in Microsoft Office Outlook allows an unauthorized attacker to perform spoofing over a network.
AnalysisAI
Insufficiently protected credentials in Microsoft Office Outlook expose authentication material over network connections, enabling unauthenticated network-positioned attackers to perform spoofing attacks contingent on victim user interaction. The flaw affects Outlook 2016, Office 2019, Office LTSC 2021, Office LTSC 2024, and Microsoft 365 Apps for Enterprise - collectively spanning nearly the entire current Outlook product line. Microsoft has released a patch; no public exploit or active exploitation (CISA KEV) has been identified at time of analysis.
Technical ContextAI
CWE-522 (Insufficiently Protected Credentials) describes a root cause where an application transmits, stores, or handles credentials without adequate protection - commonly manifesting as cleartext credential transmission, weak encoding, or authentication handshakes susceptible to interception (e.g., NTLM over unencrypted channels, HTTP Basic Auth without TLS). In Outlook's context this likely involves a mail protocol authentication exchange (SMTP, IMAP, Exchange/MAPI, or similar) where credentials are exposed in a form a network observer can capture and reuse for impersonation. The CVSS AV:N/AC:L/PR:N/UI:R vector confirms the attack is fully network-reachable with low complexity, requiring no attacker privileges, but does require a user-initiated Outlook action to trigger the vulnerable credential exchange. Affected CPE-identifiable products per EUVD-2026-56723 span Outlook 2016 build 16.0.0.0 through 16.0.5565.1000, and multiple Office suite versions (2019, LTSC 2021, LTSC 2024, M365 Apps for Enterprise) at their respective pre-patch builds.
RemediationAI
Apply the vendor-released patch without delay. For Microsoft Outlook 2016, update to build 16.0.5565.1000 or later - this is the only product line for which an explicit fixed build number is confirmed in the available data. For Microsoft Office 2019, Office LTSC 2021, Office LTSC 2024, and Microsoft 365 Apps for Enterprise, consult https://aka.ms/OfficeSecurityReleases to identify the current patched build for each channel and apply accordingly. The canonical Microsoft advisory is at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62882. As a compensating control for systems that cannot be immediately patched, enforce TLS encryption for all outbound mail protocol connections (SMTP submission, IMAP, POP3, Exchange/MAPI over HTTPS) to reduce the ability of a network observer to intercept credential exchanges; note that this mitigates interception but does not eliminate the underlying credential-protection deficiency. Additionally, network segmentation to restrict mail traffic to trusted paths can reduce attacker positioning opportunities.
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Same weakness CWE-522 – Insufficiently Protected Credentials
View allSame technique Authentication Bypass
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External POC / Exploit Code
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