The AspNetCore Remote Authenticator for SPID Allows SAML Response Signature Verification Bypass

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

9.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS

• CVE-2025-24894: 0.61% estimated exploitation activity in the next 30 days; percentile 49.08 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Description Authentication using Spid and CIE is based on the SAML2 standard which provides for two entities: Identity Provider (IdP): the system that authenticates users and provides identity information ( SAML assertions ) to the Service Provider, essentially, it is responsible for managing user credentials and identity; Service Provider (SP): The system that provides a service to the user and relies on the Identity Provider to authenticate the user, receives SAML assertions from the IdP to grant access to resources. The library spid-aspnetcorerefers to the second entity, i.e. the SP, and implements the validation logic of the SAML assertions present within the SAML response . The following is a summary diagram of an authentication flow via SAML: As shown in the diagram, the IdP, after verifying the user's credentials, generates a signed SAML response, this is propagated to the SP by the user's browser and the SP, after verifying the signature, can extract the data needed to build…

Published by the source

18 Feb 2025, 19:25 UTC

Last modified by the source

18 Feb 2025, 19:25 UTC

Source last checked

26 Oct 2026, 17:03 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-36h8-r92j-w9vw

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# Patch Next advisory brief: CVE-2025-24894

Advisory: The AspNetCore Remote Authenticator for SPID Allows SAML Response Signature Verification Bypass
IDs: CVE-2025-24894, GHSA-36h8-r92j-w9vw
Record: https://patchnext.com/advisories/cve-2025-24894 (revision 1, source checked 26 Oct 2026, 17:03 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: spid.aspnetcore.authentication 3.4.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet spid.aspnetcore.authentication: affected <= 3.3.0; fixed in 3.4.0

## Suggested inspection (read-only)
- NuGet spid.aspnetcore.authentication: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on spid.aspnetcore.authentication.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-36h8-r92j-w9vw (GitHub-reviewed advisory GHSA-36h8-r92j-w9vw lists affected ranges: NuGet spid.aspnetcore.authentication >=0 <=3.3.0)

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