CVE-2026-54782: CoreWCF Authentication Bypass Vulnerability

CRITICAL
Advisory Identifier: GHSA-xjr9-gg9q-jx3v
Share
CVSS 10.0
CWE-290 CWE-347
Published
Advisory Summary

CVE-2026-54782 is a CRITICAL (CVSS 10.0) authentication bypass vulnerability (CWE-290: Authentication Bypass by Spoofing) affecting CoreWCF libraries in the NuGet ecosystem. The issue involves authentication bypass in corewcf saml 1.1 / 2.0 token signature validation. Remediation is available by upgrading affected packages to version 1.8.1, 1.9.1.

CVE-2026-54782 at a Glance

CVE Identifier CVE-2026-54782
GHSA Identifier GHSA-xjr9-gg9q-jx3v
Severity CRITICAL
CVSS v3.1 Base Score 10.0
CWE Classification CWE-290: Authentication Bypass by Spoofing
Affected Product CoreWCF
Package Ecosystem NuGet
Published Date
Last Updated

Security Impact

CVSS: 10.0

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Changed (S:C)
Confidentiality High (C:H)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2026-54782

To remediate this vulnerability, upgrade all affected CoreWCF dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

CoreWCF.Primitives fixed: 1.8.1 
Upgrade CoreWCF.Primitives to 1.8.1
CoreWCF.Primitives fixed: 1.9.1 
Upgrade CoreWCF.Primitives to 1.9.1
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for CoreWCF.Primitives

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-54782, inspect your project dependencies for CoreWCF:

inspect dependencies for CoreWCF.Primitives

Analyze the terminal output to locate any version of CoreWCF in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.8.1), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-290: Authentication Bypass by Spoofing, where this attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks. In CoreWCF, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact Full impersonation of any principal the trusted STS could have issued an assertion for — including administrative principals when the relying party grants them via SAML claims. Affects both SAML 1.1 and SAML 2.0. #### Preconditions Relying-party service is hosted with WSFederationHttpBinding or WS2007FederationHttpBinding (or any binding that triggers FederatedSecurityTokenManager for issued-token validation), and IdentityConfiguration is wired (UseIdentityConfiguration = true). Attacker can reach the service over the network and knows the trusted STS’s public certificate (public certs are by design discoverable). ### Patches Fixed in CoreWCF v1.8.1 and v1.9.1 ### Workarounds None

CVE-2026-54782 Affected CoreWCF Versions

2 component(s)
Fixed Versions:
1.8.11.9.1
Product / Package Ecosystem Affected Versions Fixed Version
CoreWCF.Primitives
nuget/CoreWCF.Primitives
NuGet
< 1.8.1
1.8.1
CoreWCF.Primitives
nuget/CoreWCF.Primitives
NuGet
≥ 1.9.0
< 1.9.1
1.9.1

References

GitHub Advisory / Wiki ADVISORY
https://github.com/CoreWCF/CoreWCF/security/advisories/GHSA-xjr9-gg9q-jx3v
CoreWCF Source Repository REPOSITORY
https://github.com/CoreWCF/CoreWCF

Frequently Asked Questions

What is CVE-2026-54782?
CVE-2026-54782 is a security vulnerability in CoreWCF involving Authentication bypass in CoreWCF SAML 1.1 / 2.0 token signature validation under CWE-290: Authentication Bypass by Spoofing.
Which CoreWCF versions are affected?
Affected versions include releases prior to 1.8.1, 1.9.1 across affected packages: CoreWCF.Primitives.
What version fixes CVE-2026-54782?
Upgrading to 1.8.1, 1.9.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is CoreWCF.Primitives affected?
Yes, CoreWCF.Primitives is affected in releases prior to 1.8.1, 1.9.1. Upgrade your dependency to 1.8.1, 1.9.1 or later.
What is the CVSS score of CVE-2026-54782?
CVE-2026-54782 has a CVSS v3.1 base score of 10.0 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N.
What CWE is associated with CVE-2026-54782?
CVE-2026-54782 is classified under CWE-290: Authentication Bypass by Spoofing (This attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks.).
How can I check NuGet dependencies for CVE-2026-54782?
Run the dependency tree command: 'inspect dependencies for CoreWCF.Primitives'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-xjr9-gg9q-jx3v",
  "modified" : "2026-06-19T20:47:11Z",
  "published" : "2026-06-19T20:47:11Z",
  "aliases" : [ "CVE-2026-54782" ],
  "summary" : "CoreWCF: Authentication bypass in CoreWCF SAML 1.1 / 2.0 token signature validation",
  "details" : "### Impact\nFull impersonation of any principal the trusted STS could have issued an assertion for — including administrative principals when the relying party grants them via SAML claims. Affects both SAML 1.1 and SAML 2.0.\n\n#### Preconditions\nRelying-party service is hosted with WSFederationHttpBinding or WS2007FederationHttpBinding (or any binding that triggers FederatedSecurityTokenManager for issued-token validation), and IdentityConfiguration is wired (UseIdentityConfiguration = true).\nAttacker can reach the service over the network and knows the trusted STS’s public certificate (public certs are by design discoverable).\n\n### Patches\nFixed in CoreWCF v1.8.1 and v1.9.1\n\n### Workarounds\nNone",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "CoreWCF.Primitives"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.8.1"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "CoreWCF.Primitives"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.9.0"
      }, {
        "fixed" : "1.9.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/CoreWCF/CoreWCF/security/advisories/GHSA-xjr9-gg9q-jx3v"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/CoreWCF/CoreWCF"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-290", "CWE-347" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-19T20:47:11Z",
    "nvd_published_at" : null
  }
}