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CoreWCF: SamlSerializer skips SignatureValue verification when SAML signing token is not an X.509 certificate

High severity GitHub Reviewed Published Jun 16, 2026 in CoreWCF/CoreWCF • Updated Jun 19, 2026

Package

nuget CoreWCF.Primitives (NuGet)

Affected versions

< 1.8.1
>= 1.9.0, < 1.9.1

Patched versions

1.8.1
1.9.1

Description

Impact

When a service is configured to validate SAML tokens using a method other than X.509 certificate signing, the final signature verification is skipped.

Preconditions

The service is configured to authenticate using SAML tokens and an out of band token resolver (commonly the IssuerTokenResolver of IssuedTokenServiceCredential) holds a non-X.509 SecurityToken whose key identifier the attacker can reference in the assertion’s <KeyInfo> - for example a BinarySecretSecurityToken representing the symmetric proof key issued by a WS-Trust symmetric-key holder-of-key STS.

Patches

Fixed in CoreWCF v1.8.1 and v1.9.1

Workarounds

None

References

@mconnew mconnew published to CoreWCF/CoreWCF Jun 16, 2026
Published to the GitHub Advisory Database Jun 19, 2026
Reviewed Jun 19, 2026
Last updated Jun 19, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(5th percentile)

Weaknesses

Insufficient Verification of Data Authenticity

The product does not sufficiently verify the origin or authenticity of data, in a way that causes it to accept invalid data. Learn more on MITRE.

Improper Verification of Cryptographic Signature

The product does not verify, or incorrectly verifies, the cryptographic signature for data. Learn more on MITRE.

CVE ID

CVE-2026-54774

GHSA ID

GHSA-rpj7-hr7h-w6p9

Source code

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