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CoreWCF NetNamedPipe transport accepts attach to a pre-existing named pipe instance

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

Package

nuget CoreWCF.NetNamedPipe (NuGet)

Affected versions

< 1.8.1
>= 1.9.0, < 1.9.1

Patched versions

1.8.1
1.9.1

Description

Impact

CoreWCF NetNamedPipe transport accepts attach to a pre-existing named pipe instance, allowing local interception of NetNamedPipe traffic. NetNamedPipe creates a shared memory object based on the listening url, then generated a unique GUID for the named pipe it will be using and saves this to the shared memory object. Then it creates the named pipe to listen for clients. This requires an attacker to race the service and create the named pipe between the service publishing the GUID to the shared memory location (which the attacker needs to read) and the service creating the named pipe itself.

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

Moderate

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
Local
Attack complexity
High
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
Low

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:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L

EPSS score

Weaknesses

Time-of-check Time-of-use (TOCTOU) Race Condition

The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. Learn more on MITRE.

Improper Initialization

The product does not initialize or incorrectly initializes a resource, which might leave the resource in an unexpected state when it is accessed or used. Learn more on MITRE.

CVE ID

CVE-2026-54777

GHSA ID

GHSA-6jj2-4q5c-x8g6

Source code

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