EUVD-2026-43995
GHSA-cqjp-pw74-x785
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Remote unauthenticated crash of a network-exposed AD FS service with no user interaction (AV:N/AC:L/PR:N/UI:N); impact is availability-only, so C:N/I:N/A:H.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
2DescriptionCVE.org
Stack-based buffer overflow in Active Directory Federation Services (AD FS) allows an unauthorized attacker to deny service over a network.
AnalysisAI
Denial of service in Microsoft Active Directory Federation Services (AD FS) lets a remote, unauthenticated attacker crash the service by triggering a stack-based buffer overflow (CWE-121) over the network. The flaw affects AD FS as shipped across a broad range of Windows client and server builds (Windows 10/11 and Windows Server 2012 through 2025). …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires network reachability to a running AD FS service endpoint (typically the federation/token-issuance or metadata endpoints, often exposed externally via the Web Application Proxy); the CVSS vector AV:N/AC:L/PR:N/UI:N indicates no authentication, no user interaction and low complexity against a reachable AD FS instance. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 base score is 7.5 (High) driven entirely by availability impact: AV:N/AC:L/PR:N/UI:N means the attacker needs only network reach to an AD FS endpoint, with no authentication, no user interaction and low complexity - a realistically triggerable remote DoS. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker with network access to an internet-facing AD FS endpoint sends a crafted request whose oversized field overflows a fixed-size stack buffer, crashing the AD FS process. Because no authentication or user interaction is required (AV:N/AC:L/PR:N/UI:N), repeated requests can keep the service down, blocking single sign-on to Microsoft 365 and other relying parties. … |
| Remediation | Apply the Microsoft security update for CVE-2026-54983 to all systems running the AD FS role; Microsoft has released a patch, so the primary action is to install the corresponding monthly cumulative/security update for each affected Windows Server or client build as listed in the vendor advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-54983 (exact fixed build numbers are per-platform in that Update Guide entry - no single fixed version applies across all products). … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify and document all Active Directory Federation Services installations across Windows 10, 11, Server 2012 R2, Server 2016, Server 2019, Server 2022, and Server 2025 environments and obtain the Microsoft-released patch. …
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Same weakness CWE-121 – Stack-based Buffer Overflow
View allSame technique Buffer Overflow
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External POC / Exploit Code
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