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Critical

Improper Authorization Information Disclosure in Microsoft Exchange Online

IdentifiersCVE-2026-48579CWE-285· Improper Authorization

CVE-2026-48579 is an improper authorization vulnerability in Microsoft Exchange Online. According to the provided advisory content, the flaw allows an unauthorized attacker to disclose information over a network. The available information indicates this is a network-reachable issue in Microsoft's hosted Exchange Online service and does not require prior authentication or user interaction. No further technical detail about the affected component, request path, or vulnerable function is currently available in the provided content.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation allows an unauthorized remote attacker to access and disclose information from Microsoft Exchange Online over the network. The provided CVSS v3.1 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N) indicates high confidentiality impact and no availability impact. The source material also lists high integrity impact in the vector, but the narrative description specifically emphasizes information disclosure; no additional verified detail is provided to explain the integrity impact.

Mitigation

If you can’t patch tonight, do this now.

No customer mitigation is required. Microsoft has already fully mitigated the issue in the hosted Exchange Online service, and the advisory indicates there is no action for customers to take.

Remediation

Patch, then assume compromise.

No customer remediation is required. Microsoft states the vulnerability has already been fully mitigated in the Exchange Online service.
PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType
Microsoft CorporationExchange Onlineapplication

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

6 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

6 SOURCESView more in app
What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.
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Exposure mapping

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Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity5

Community discussion across Reddit, Mastodon, and other social sources.

EXTERNAL REFERENCES
MITRE CVE
cve.org · CVE-2026-48579
NVD
nvd.nist.gov/vuln/detail/CVE-2026-48579
MITRE CWE · CWE-285
Improper Authorization
Vendor Advisory
msrc.microsoft.com/update-guide/vulnerability/CVE-2026-48579