Microsoft AD FS CVE-2026-96252

Exploitation requires network reachability to an AD FS federation endpoint that processes signed tokens; per the CVSS vector (AV:N/AC:L/PR:N/UI:N) no authentication, user interaction, or special privileges are needed against affected unpatched builds. The core prerequisite is that the target runs an AD FS role on an unpatched Windows Server version in the affected ranges (e.g., Server 2012 R2 <6.3.9600.23470, Server 2016 <10.0.14393.9612, Server 2019 <10.0.17763.9376, Server 2022 <10.0.20348.5761, Server 2025 <10.0.26100.33650). Limiting factors: the AD FS role must actually be installed and internet/network-exposed, and successful spoofing depends on the attacker being able to craft a token the flawed verification logic accepts; organizations not using AD FS federation are not exposed.

This is a genuine high-priority vulnerability, not an inflated CVSS score. The CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N) describes a network-reachable, low-complexity, unauthenticated attack with high confidentiality and integrity impact (C:H/I:H), and the CWE-347 signature-verification weakness combined with the 'Jwt Attack' and 'Authentication Bypass' tags points to token/signature forgery enabling identity spoofing against a federation service - a high-value target. The SSVC framework reinforces this concern: Automatable=yes and Technical Impact=total indicate that a working exploit could be reliably reproduced at scale with complete compromise of the affected trust function. However, signals are mixed on imminence: SSVC Exploitation=none, and there is no CISA KEV listing and no public POC, so there is currently no public exploit identified at time of analysis. This is therefore a 'patch urgently but not yet actively exploited' situation - the combination of unauthenticated network access, automatable exploitation, and total technical impact against an identity-federation component means it should be prioritized despite the absence of confirmed in-the-wild activity. Note the A:N: this is a spoofing/forgery flaw, not a denial-of-service, consistent with the description.

A remote, unauthenticated attacker crafts a token (e.g., a JWT or SAML assertion) with a forged or improperly validated cryptographic signature and submits it to an AD FS endpoint, which fails to properly verify the signature and accepts it as legitimate. This lets the attacker spoof another user's or service's identity and obtain federated authentication to downstream relying-party applications. No public exploit code has been identified, but SSVC rates the issue as automatable with total technical impact.