CVE-2026-63523: Skype for Business Spoofing Vulnerability

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% 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-79

Description

Improper neutralization of input during web page generation ('cross-site scripting') in Skype for Business allows an unauthorized attacker to perform spoofing 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-2026-63523

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