# CVE-2026-54784: CoreWCF: SPNEGO SecurityContextToken proof key wrapped without confidentiality

> An attacker can impersonate authenticated users and decrypt traffic due to insufficient protection of SPNEGO proof keys in CoreWCF.

- **Severity:** High 7.4 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/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-2288-8h3r-cqgg

## What is CVE-2026-54784?

CVE-2026-54784 is a high-severity 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. In version 1.9.0, CoreWCF SPNEGO SecurityContextToken negotiation can expose the proof key recovered from the RSTR when TransportWithMessageCredential with Windows client credentials and session establishment are used, allowing an observer to impersonate the authenticated Windows principal and decrypt or forge WS-SecureConversation traffic. This issue is fixed in version 1.9.1.

Weakness: CWE-523 (Unprotected Transport of Credentials), CWE-311 (Missing Encryption of Sensitive Data)

## Which versions are affected by CVE-2026-54784?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `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-2026-54784?

Upgrade CoreWCF.Primitives to 1.9.1 or later.

## Is CVE-2026-54784 being exploited?

There is no known exploitation of CVE-2026-54784 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-54784 and fix it if it is affected.

What it is: CVE-2026-54784 is a high-severity 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-2026-54784 in the wild and no public exploit code.

Affected packages and fixed versions:
- 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-2026-54784/ (Markdown: https://insights.sbomify.com/CVE-2026-54784/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-54784
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-54784
- OSV: https://osv.dev/vulnerability/CVE-2026-54784

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-54784/
Summaries are generated and may contain mistakes; the official description above is the record.