CVE-2026-66305: CWE-603: Use of Client-Side Authentication in Microsoft Skype for Business Server 2015 CU13
CVE-2026-66305 is a vulnerability in Microsoft Skype for Business Server 2015 CU13 (version 9319.0) involving the use of client-side authentication. This flaw allows an authorized attacker to perform spoofing attacks over a network. The vulnerability has a high severity rating with a CVSS score of 7.1. An official fix is available from Microsoft to address this issue.
AI Analysis
Technical Summary
This vulnerability (CWE-603) in Skype for Business Server 2015 CU13 arises from the use of client-side authentication, which can be exploited by an authorized attacker to spoof identities over a network. The CVSS 3.1 vector indicates the attack requires network access, low attack complexity, and privileges, with no user interaction needed. The impact includes limited confidentiality loss and high integrity impact, with no availability impact. Microsoft has published an official fix for this vulnerability.
Potential Impact
An authorized attacker can exploit this vulnerability to spoof identities within the Skype for Business Server 2015 environment, potentially leading to unauthorized actions or impersonation. Confidentiality impact is limited, but integrity impact is high. There is no impact on availability. No known exploits are reported in the wild at this time.
Mitigation Recommendations
An official fix is available from Microsoft. Users should apply the patch provided in the Microsoft Security Response Center advisory to remediate this vulnerability. Since the product is not a cloud service, remediation requires applying the update to affected systems.
CVE-2026-66305: CWE-603: Use of Client-Side Authentication in Microsoft Skype for Business Server 2015 CU13
Description
CVE-2026-66305 is a vulnerability in Microsoft Skype for Business Server 2015 CU13 (version 9319.0) involving the use of client-side authentication. This flaw allows an authorized attacker to perform spoofing attacks over a network. The vulnerability has a high severity rating with a CVSS score of 7.1. An official fix is available from Microsoft to address this issue.
CVSS v3.1
Score 7.1high
Affected software
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability (CWE-603) in Skype for Business Server 2015 CU13 arises from the use of client-side authentication, which can be exploited by an authorized attacker to spoof identities over a network. The CVSS 3.1 vector indicates the attack requires network access, low attack complexity, and privileges, with no user interaction needed. The impact includes limited confidentiality loss and high integrity impact, with no availability impact. Microsoft has published an official fix for this vulnerability.
Potential Impact
An authorized attacker can exploit this vulnerability to spoof identities within the Skype for Business Server 2015 environment, potentially leading to unauthorized actions or impersonation. Confidentiality impact is limited, but integrity impact is high. There is no impact on availability. No known exploits are reported in the wild at this time.
Mitigation Recommendations
An official fix is available from Microsoft. Users should apply the patch provided in the Microsoft Security Response Center advisory to remediate this vulnerability. Since the product is not a cloud service, remediation requires applying the update to affected systems.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- microsoft
- Date Reserved
- 2026-07-24T18:06:51.294Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- official-fix
- Vendor Advisory Urls
- [{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66305","vendor":"Microsoft"}]
Threat ID: 6aa059e1acd9273b4913b800
Added to database: 09/08/2026, 18:54:25 UTC
Last enriched: 09/08/2026, 19:07:09 UTC
Last updated: 09/09/2026, 02:17:36 UTC
Views: 10
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