CVE-2026-48579
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedImproper authorization in Microsoft Exchange Online allows an unauthorized attacker to disclose information over a network.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceImproper authorization vulnerability in Microsoft Exchange Online enables an unauthorized remote attacker to access and disclose sensitive information over a network. The flaw appears to stem from insufficient access control checks that fail to properly validate user permissions before granting information access.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE dataall versionsCVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Confirm Exchange Online usageVerify your organization uses Microsoft Exchange Online by checking the Microsoft 365 admin center under 'Exchange' or by running Get-OrganizationConfig in Exchange Online PowerShell to confirm the service typeAffected if The organization uses Microsoft Exchange Online (all versions are affected)
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Review mailbox delegate permissionsUse Exchange Online PowerShell: Get-Mailbox -ResultSize Unlimited | Get-MailboxPermission to list all mailbox delegations, then identify accounts with FullAccess or Send-As permissions granted to unexpected usersAffected if Mailboxes have delegate permissions granted to unauthorized or unexpected users without proper authorization checks
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Audit sharing settingsUse Get-SharingPolicy in Exchange Online PowerShell to review all sharing policies, and check Get-OrganizationConfig | Select-Object SharingPolicyEnabled to see if organizational sharing is enabledAffected if Sharing policies allow external access or overly permissive internal sharing without proper access controls
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Review Azure AD sign-in logs for unauthorized accessIn Microsoft 365 admin center, navigate to Azure Active Directory > Sign-in logs, or use Get-AzureADAuditSignInLogs in Azure AD PowerShell module to search for suspicious mailbox access from unexpected locations or accountsAffected if Sign-in logs show mailbox access by unauthorized users or from unexpected IP addresses
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Check mailbox audit logsUse Search-MailboxAuditLog in Exchange Online PowerShell with date ranges to identify MailboxLogin events or Access events by users who should not have access, or enable mailbox auditing if not already enabledAffected if Mailbox audit logs reveal unauthorized access to sensitive mailboxes or folders
An organization is affected if they use Microsoft Exchange Online and evidence shows unauthorized users accessed mailboxes or sensitive information due to insufficient access control validation.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataMonitor Microsoft's security advisories for Exchange Online patches; review sharing settings and mailbox permissions to ensure least-privilege access until a fix is deployed by Microsoft.
- Consultation4.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,912.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-48579 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-48579 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data