CVE-2026-54784
CoreWCF: SPNEGO SecurityContextToken proof key wrapped without confidentiality
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
CoreWCF: SPNEGO SecurityContextToken proof key wrapped without confidentiality
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.
- Record
CVE-2026-54784- CVSS 3.1
- 7.4 High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N - Weakness
- CWE-311, CWE-523
- Updated
- 2026-11-02
EUVDEUVD-2026-42471
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.
- Record
EUVD-2026-42471- CVSS 3.1
- 7.4 High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-2288-8h3r-cqgg
CoreWCF: SPNEGO SecurityContextToken proof key wrapped without confidentiality
Impact
When the proof key recovered from the RSTR can be observed by a party that is not the legitimate client, that party can impersonate the authenticated Windows principal for the lifetime of the SCT (default ~10 hours) and decrypt or forge any subsequent WS‑SecureConversation traffic that uses keys derived from the SCT.
Preconditions
Using security mode TransportWithMessageCredential with client credential type Windows, along with session establishment (which triggers use of WS-SecureConversation).
Patches
Fixed in CoreWCF v1.9.1
Workarounds
Ensure communication is protected by SSL/TLS to prevent capturing of SCT negotiation handshake.
- Record
GHSA-2288-8h3r-cqgg- CVSS 3.1
- 7.4 High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N - Weakness
- CWE-311, CWE-523
- Updated
- 2026-11-02
NVD
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.
- Record
CVE-2026-54784- CVSS 3.1
- 7.4 High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N - Weakness
- CWE-311, CWE-523
- Updated
- 2026-11-02
OSV
CoreWCF: SPNEGO SecurityContextToken proof key wrapped without confidentiality
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.
- Record
CVE-2026-54784- CVSS 3.1
- 7.4 High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N - Weakness
- CWE-311, CWE-523
- Updated
- 2026-11-02
OSVGHSA-2288-8h3r-cqgg
CoreWCF: SPNEGO SecurityContextToken proof key wrapped without confidentiality
Impact
When the proof key recovered from the RSTR can be observed by a party that is not the legitimate client, that party can impersonate the authenticated Windows principal for the lifetime of the SCT (default ~10 hours) and decrypt or forge any subsequent WS‑SecureConversation traffic that uses keys derived from the SCT.
Preconditions
Using security mode TransportWithMessageCredential with client credential type Windows, along with session establishment (which triggers use of WS-SecureConversation).
Patches
Fixed in CoreWCF v1.9.1
Workarounds
Ensure communication is protected by SSL/TLS to prevent capturing of SCT negotiation handshake.
- Record
GHSA-2288-8h3r-cqgg- CVSS 3.1
- 7.4 High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N - Weakness
- CWE-311, CWE-523
- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
CoreWCF.PrimitivesNuGet |
1.9.0 up to 1.9.1 | 1.9.1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-54784 is a high vulnerability (CVSS 7.4) in Corewcf, published June 19, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.27%, the 19th percentile. Fixed in CoreWCF.Primitives 1.9.1.
References
github.com/CoreWCF/CoreWCF/security/advisories/GHSA-2288-8h3r-cqgg
nvd.nist.gov/vuln/detail/CVE-2026-54784