CVE-2026-96222
Description
Improper certificate validation in Active Directory Federation Services (AD FS) allows an unauthorized attacker to perform spoofing over a network.
Statement
An improper certificate validation flaw of IMPORTANT severity was found in the .NET System.Security.Cryptography.Xml library as shipped in the dotnet8.0 packages of Red Hat Enterprise Linux 8, 9, and 10, Red Hat In-Vehicle OS, and Red Hat Hardened Images. The KeyInfoX509Data API can accept serialized certificate formats containing attacker-controlled chain metadata instead of requiring a plain X.509 certificate, enabling certificate-forgery and token-spoofing paths. A remote, unauthenticated attacker could exploit this weakness, which Microsoft describes as a spoofing vulnerability in Active Directory Federation Services (AD FS), to forge certificates and spoof signed content or tokens, compromising the confidentiality and integrity of certificate and token validation. Exploitation requires high attack complexity, and the Red Hat CVSS 3.1 score of 7.4 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N) matches the upstream assessment. Fixes for the affected Red Hat products are delegated to the upstream .NET correction, which is being pursued for all affected streams.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.4 | N/A | 7.4 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C
Red Hat CVSS v3 Score Explanation
Microsoft CNA CVSS from pre-release advisory
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