PT-2026-34051 · Microsoft+3 · Asp.Net Core+3
CVE-2026-40372
·
Published
2026-04-21
·
Updated
2026-06-27
CVSS v3.1
9.4
Critical
| Vector | AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N |
Name of the Vulnerable Software and Affected Versions
Microsoft.AspNetCore.DataProtection versions 10.0.0 through 10.0.6
Description
An issue in the
Microsoft.AspNetCore.DataProtection library involves the improper verification of cryptographic signatures. This flaw allows an unauthorized remote attacker to forge authentication cookies and other protected payloads, which can be used to decrypt certain data and elevate privileges to SYSTEM level over a network. The issue is specifically exploitable on non-Windows operating systems, such as Linux and macOS, or when the net462 or netstandard2.0 target framework assets are consumed. Real-world analysis indicates that attackers have used this flaw to forge authentication tokens to gain administrative privileges and perform lateral movement within affected applications.Recommendations
Upgrade
Microsoft.AspNetCore.DataProtection to version 10.0.7 or later and redeploy the application.
Rotate the DataProtection key ring to invalidate any legitimately-signed tokens issued to attackers during the vulnerable window.
Audit and rotate application-level long-lived artifacts created during the vulnerable window, such as API keys, refresh tokens, access tokens, password reset links, or email-confirmation tokens.
Rotate any long-lived secrets, such as database connection strings or third-party API keys, that were stored in plaintext inside IDataProtector.Protect output.
Review web server logs for anomalous high-volume traffic against endpoints that accept protected payloads, such as auth cookies, antiforgery tokens, or state parameters.Fix
LPE
DoS
Improper Verification of Cryptographic Signature
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Weakness Enumeration
Related Identifiers
Affected Products
Asp.Net Core
Linuxmint
Red Os
Ubuntu