# CVE-2026-54782: CoreWCF: Authentication bypass in CoreWCF SAML 1.1 / 2.0 token signature validation

> An unauthenticated attacker can impersonate any principal in CoreWCF applications using federated bindings due to flawed SAML token signature validation.

- **Severity:** Critical 10.0 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 8 Jul 2026
- **Updated:** 10 Jul 2026
- **Also known as:** GHSA-xjr9-gg9q-jx3v

## What is CVE-2026-54782?

CVE-2026-54782 is a critical authentication bypass vulnerability in CoreWCF, published on 8 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

CoreWCF is a port of the service side of Windows Communication Foundation (WCF) to .NET Core. Prior to 1.8.1 and 1.9.1, CoreWCF SAML 1.1 and SAML 2.0 token validation does not correctly resolve the issuer signing key or require signed tokens when IdentityConfiguration is used with federated bindings, allowing an unauthenticated remote attacker to impersonate any principal the trusted STS could issue. This issue is fixed in versions 1.8.1 and 1.9.1.

Weakness: CWE-347 (Improper Verification of Cryptographic Signature), CWE-290 (Authentication Bypass by Spoofing)

## Which versions are affected by CVE-2026-54782?

4 open source packages ship an affected version, including CoreWCF.Primitives.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `CoreWCF.Primitives` | NuGet | All versions | 1.8.1 |
| `CoreWCF.Primitives` | NuGet | All versions | 1.8.1 |
| `CoreWCF.Primitives` | NuGet | From 1.9.0 | 1.9.1 |
| `CoreWCF.Primitives` | NuGet | From 1.9.0 | 1.9.1 |

## How do I fix CVE-2026-54782?

Upgrade CoreWCF.Primitives to a fixed version for your release line: 1.8.1 or 1.9.1.

## Is CVE-2026-54782 being exploited?

There is no known exploitation of CVE-2026-54782 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-54782 and fix it if it is affected.

What it is: CVE-2026-54782 is a critical authentication bypass vulnerability in CoreWCF, published on 8 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-54782 in the wild and no public exploit code.

Affected packages and fixed versions:
- CoreWCF.Primitives (NuGet): affected all versions; fixed in 1.8.1
- CoreWCF.Primitives (NuGet): affected all versions; fixed in 1.8.1
- CoreWCF.Primitives (NuGet): affected from 1.9.0; fixed in 1.9.1
- CoreWCF.Primitives (NuGet): affected from 1.9.0; fixed in 1.9.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-54782/ (Markdown: https://insights.sbomify.com/CVE-2026-54782/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-54782
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-54782
- OSV: https://osv.dev/vulnerability/CVE-2026-54782

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-54782/
Summaries are generated and may contain mistakes; the official description above is the record.