Vulnerability · Published Jul 8, 2026 · Assigned by GitHub_M

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

High 7.4

In plain English

A high-severity security flaw in CoreWCF from CoreWCF. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 20% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.4High

Exploit odds (30 days)0.3%top 80.3% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
NuGet	corewcf.primitives	1.9.1	GHSA-2288-8h3r-cqgg

Affected products (as reported)

Vendor	Product	Versions
CoreWCF	CoreWCF	>= 1.9.0, < 1.9.1

Weakness: CWE-311, CWE-523 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

References

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