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CVE-2026-66306: Skype for Business Information Disclosure Vulnerability

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.9% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-08 · updated 2026-10-31
• Weakness: CWE-209

Description

Generation of error message containing sensitive information in Skype for Business allows an unauthorized attacker to disclose information over a network.

Affected products

• Microsoft Skype for Business Server 2019 CU7: 2015-cumulative_update_13, 2015-cumulative_update_13_hotfix_2, 2019-cumulative_update_8, 2019-cumulative_update_8_hotfix1, 2019-cumulative_update_8_hotfix2
• Microsoft Skype For Business Server Subscription Edition: 7.0.2046.849
• Microsoft Skype for Business Server 2015 CU13: from 9319.0 before 6.0.9319.885 — fixed in 6.0.9319.885
• Microsoft Skype for Business Server 2019 CU8: from 2046.0 before 7.0.2046.569 — fixed in 7.0.2046.569
• Microsoft Skype for Business Server Subscription Edition CU1: from 2046.0 before 7.0.2046.879 — fixed in 7.0.2046.879

How to fix

Upgrade to a fixed version: Microsoft Skype for Business Server 2015 CU13 6.0.9319.885; Microsoft Skype for Business Server 2019 CU8 7.0.2046.569; Microsoft Skype for Business Server Subscription Edition CU1 7.0.2046.879. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66306

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