CVE-2026-97788: Active Directory Federation Services (AD FS) Information Disclosure Vulnerability

Severity: high (CVSS 7.5 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: 2026-10-13 · updated 2026-10-31
Weakness: CWE-203

Description

Observable discrepancy in Active Directory Federation Services (AD FS) allows an unauthorized attacker to disclose information over a network.

Affected products

Microsoft .NET Framework: 4.8.1, 4.8, 4.6.2, 4.7, 4.7.1, 4.7.2 (+1)
Microsoft Windows 10 1607: before 10.0.14393.9612 — fixed in 10.0.14393.9612
Microsoft Windows 10: before 10.0.17763.9376 — fixed in 10.0.17763.9376
Microsoft Windows 10: before 10.0.19044.7807 — fixed in 10.0.19044.7807
Microsoft Windows 10: before 10.0.19045.7807 — fixed in 10.0.19045.7807
Microsoft Windows 11: before 10.0.22631.7652 — fixed in 10.0.22631.7652
Microsoft Windows 11: before 10.0.26100.9711 — fixed in 10.0.26100.9711
Microsoft Windows 11 25H2: before 10.0.26200.9711 — fixed in 10.0.26200.9711
Microsoft Windows 11 version 26H1: before 10.0.28000.3231 — fixed in 10.0.28000.3231
Microsoft Windows 11 26H2: before 10.0.26300.9711 — fixed in 10.0.26300.9711
Microsoft Windows Server 2012: r2
Microsoft Windows Server 2016: before 10.0.14393.9612 — fixed in 10.0.14393.9612
Microsoft Windows Server 2019: before 10.0.17763.9376 — fixed in 10.0.17763.9376
Microsoft Windows Server 2022: before 10.0.20348.5761 — fixed in 10.0.20348.5761
Microsoft Windows Server 2025: before 10.0.26100.33650 — fixed in 10.0.26100.33650
Microsoft .NET Framework 3.5: from 3.5.0 before 2.0.50727.9188 AND 3.0.30729.9171 — fixed in 2.0.50727.9188 AND 3.0.30729.9171
Microsoft .NET Framework 3.5 AND 4.6.2/4.7/4.7.1/4.7.2: from 3.0.0.0 before 2.0.50727.8987 AND 3.0.30729.8982 AND 4.7.4150.0 — fixed in 2.0.50727.8987 AND 3.0.30729.8982 AND 4.7.4150.0
Microsoft .NET Framework 3.5 AND 4.7.2: from 4.7.0 before 2.0.50727.9073 AND 3.0.30729.9070 AND 4.7.4150.0 — fixed in 2.0.50727.9073 AND 3.0.30729.9070 AND 4.7.4150.0
Microsoft .NET Framework 3.5 AND 4.8: from 4.8.0 before 2.0.50727.9073 AND 3.0.30729.9070 AND 4.8.4811.0 — fixed in 2.0.50727.9073 AND 3.0.30729.9070 AND 4.8.4811.0
Microsoft .NET Framework 3.5 AND 4.8.1: from 4.8.1 before 2.0.50727.9188 AND 3.0.30729.9171 AND 4.8.9363.0 — fixed in 2.0.50727.9188 AND 3.0.30729.9171 AND 4.8.9363.0
Microsoft .NET Framework 4.6.2/4.7/4.7.1/4.7.2: from 4.7.0 before 4.7.4150.0 — fixed in 4.7.4150.0
Microsoft .NET Framework 4.8: from 4.8.0 before 4.8.4811.0 — fixed in 4.8.4811.0
Microsoft .NET Framework 4.8.1: from 4.8.0.0 before 4.8.9363.0 — fixed in 4.8.9363.0
Microsoft Windows 10 1607: from 10.0.14393.0 before 10.0.14393.9612 — fixed in 10.0.14393.9612
Microsoft Windows 10: from 10.0.17763.0 before 10.0.17763.9376 — fixed in 10.0.17763.9376
Microsoft Windows 10: from 10.0.19044.0 before 10.0.19044.7807 — fixed in 10.0.19044.7807
Microsoft Windows 10: from 10.0.19045.0 before 10.0.19045.7807 — fixed in 10.0.19045.7807
Microsoft Windows 11: from 10.0.22631.0 before 10.0.22631.7652 — fixed in 10.0.22631.7652
Microsoft Windows 11: from 10.0.26100.0 before 10.0.26100.9711 — fixed in 10.0.26100.9711
Microsoft Windows 11 25H2: from 10.0.26200.0 before 10.0.26200.9711 — fixed in 10.0.26200.9711

How to fix

Upgrade to a fixed version: Microsoft Windows 10 1607 10.0.14393.9612; Microsoft Windows 10 10.0.17763.9376; Microsoft Windows 10 10.0.19044.7807; Microsoft Windows 10 10.0.19045.7807; Microsoft Windows 11 10.0.22631.7652; Microsoft Windows 11 10.0.26100.9711; Microsoft Windows 11 25H2 10.0.26200.9711; Microsoft Windows 11 version 26H1 10.0.28000.3231; Microsoft Windows 11 26H2 10.0.26300.9711; Microsoft Windows Server 2016 10.0.14393.9612; Microsoft Windows Server 2019 10.0.17763.9376; Microsoft Windows Server 2022 10.0.20348.5761. Check the vendor advisory for mitigations.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-97788

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