Emerging Threat: (CVE-2026-40372) ASP.NET Core Privilege Escalation via Signature Bypass
CVE-2026-40372 is an elevation of privilege vulnerability in ASP.NET Core caused by improper verification of cryptographic signatures in the Data Protection library. The flaw sits in the HMAC validation routine of the managed authenticated encryptor, where a defective comparison lets an attacker submit a forged payload that the application accepts as legitimately signed. The vulnerability carries a CVSS v3.1 base score of 8.1 (Important), as assigned by Microsoft in the official advisory.