EUVD-2026-56417
GHSA-255v-3pqf-6g77
Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
Low-privilege network credential is sufficient; missing authorization enables high-integrity writes with no confidentiality or availability impact and no scope change.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
3DescriptionCVE.org
Missing authorization in Microsoft Exchange Server allows an authorized attacker to bypass a security feature over a network.
AnalysisAI
Missing authorization in Microsoft Exchange Server allows authenticated low-privilege network users to bypass a security feature, achieving high-integrity impact without requiring elevated credentials or user interaction. Rooted in CWE-862, Exchange fails to enforce a required authorization check on at least one network-accessible endpoint, enabling unauthorized high-integrity modifications - such as changes to mailbox permissions, transport rules, or security policy - by any valid account holder. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires a valid low-privilege Exchange account credential (confirmed by CVSS PR:L), ruling out unauthenticated external attackers. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 6.5 score reflects a genuine medium-severity issue: network-accessible, low complexity, low-privilege, and no user interaction required, but bounded by the PR:L requirement and a scope-unchanged impact limited entirely to integrity. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Apply Microsoft's released patches immediately by upgrading to the following fixed builds: Exchange 2019 CU15 to build 15.02.1748.049 or later, Exchange 2019 CU14 to build 15.02.1544.044 or later, Exchange 2016 CU23 to build 15.01.2507.072 or later, and Exchange Subscription Edition RTM to build 15.02.2562.046 or later. … Detailed patch versions, workarounds, and compensating controls in full report. |
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Same weakness CWE-862 – Missing Authorization
View allSame technique Authentication Bypass
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External POC / Exploit Code
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