CVE-2026-66304Network attack vector

Unauthenticated information disclosure via server-side request forgery

Published Sep 8, 2026 · Updated Sep 10, 2026

Server-side request forgery in Microsoft Skype for Business Server allows remote attackers to disclose information over a network. Microsoft has not published the affected component or the operation that accepts attacker-controlled request destinations. Skype for Business Server 2015 CU13 before 6.0.9319.885, Server 2019 CU8 before 7.0.2046.569, and Subscription Edition CU1 before 7.0.2046.879 are affected; no authentication or user interaction is required.

CVSS severity7.5
High
EPSS probability0.71%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Server-side request forgery in Microsoft Skype for Business Server allows remote attackers to disclose information over a network. Microsoft has not published the affected component or the operation that accepts attacker-controlled request destinations. Skype for Business Server 2015 CU13 before 6.0.9319.885, Server 2019 CU8 before 7.0.2046.569, and Subscription Edition CU1 before 7.0.2046.879 are affected; no authentication or user interaction is required.

The record

CVE
CVE-2026-66304
Published
Sep 8, 2026
Updated
Sep 10, 2026
Vendor
Microsoft
Product
Skype for Business Server Subscription Edition
Classifications
CWE-918, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 10, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2046.0 <7.0.2046.879

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Microsoft · Skype for Business Server Subscription Editionversion=2046.0 <7.0.2046.879
Microsoft · Skype for Business Serverversion=2046.0 <7.0.2046.569; version=9319.0 <6.0.9319.885

Published CVSS scores

7.5MicrosoftCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-918Server-Side Request Forgery (SSRF)
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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