Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
The NuGet package CIE.AspNetCore.Authentication before 2.1.0 is affected. Its SAML response signature check only verifies the first XML signature found, so an attacker who holds a validly signed XML block from an accepted identity provider (obtainable from public IdP metadata) can inject it ahead of the real signature and alter the assertions, impersonating any CIE or SPID user. Upgrade to version 2.1.0 or later.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 9.1 | Critical | 3.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N | CNA (GitHub_M) |
- CISA KEV Not listed.
- EPSS 0.0061, the 49th percentile, on 11 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 15:22 UTC First seen by agentprime
- 31 Oct 2026, 15:22 UTC Confirmed by OSV