CVE-2026-54776: CoreWCF Unix Domain Socket PosixIdentity Transport Vulnerability

MODERATE
Advisory Identifier: GHSA-wjpq-6766-7f5j
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CVSS 4.4
CWE-306
Published
Advisory Summary

CVE-2026-54776 is a MODERATE (CVSS 4.4) unix domain socket posixidentity transport vulnerability (CWE-306: Missing Authentication for Critical Function) affecting CoreWCF libraries in the NuGet ecosystem. The issue involves unix domain socket posixidentity transport accepts connections that skip the security upgrade. Remediation is available by upgrading affected packages to version 1.8.1, 1.9.1.

CVE-2026-54776 at a Glance

CVE Identifier CVE-2026-54776
GHSA Identifier GHSA-wjpq-6766-7f5j
Severity MODERATE
CVSS v3.1 Base Score 4.4
CWE Classification CWE-306: Missing Authentication for Critical Function
Affected Product CoreWCF
Package Ecosystem NuGet
Published Date
Last Updated

Security Impact

CVSS: 4.4

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

Attack Vector Local (AV:L)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2026-54776

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.UnixDomainSocket fixed: 1.8.1 
Upgrade CoreWCF.UnixDomainSocket to 1.8.1
CoreWCF.UnixDomainSocket fixed: 1.9.1 
Upgrade CoreWCF.UnixDomainSocket 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.UnixDomainSocket

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-54776, inspect your project dependencies for CoreWCF:

inspect dependencies for CoreWCF.UnixDomainSocket

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-306: Missing Authentication for Critical Function, where the product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources. 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 A CoreWCF service hosted on Unix Domain Sockets with the PosixIdentity client credential type (UnixDomainSocketBinding with Security.Mode = TransportCredentialOnly and Security.Transport.ClientCredentialType = PosixIdentity) does not require the client to perform the application/unixposix stream upgrade before dispatching messages. ### Patches Fixed in CoreWCF v1.8.1 and v1.9.1 ### Workarounds Restrict filesystem access to the UDS socket file using owner/group/mode (e.g. chmod 0660 plus a dedicated group) so that only the POSIX users who are already authorized to invoke the service can connect at all. This makes the missing-upgrade behaviour equivalent to the operating system’s filesystem permissions instead of relying on framing-layer identity checks. Avoid relying on ServiceSecurityContext.PrimaryIdentity for authorization decisions, or back it up with an authentication-required authorization policy that rejects anonymous principals.

CVE-2026-54776 Affected CoreWCF Versions

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

References

GitHub Advisory / Wiki ADVISORY
https://github.com/CoreWCF/CoreWCF/security/advisories/GHSA-wjpq-6766-7f5j
CoreWCF Source Repository REPOSITORY
https://github.com/CoreWCF/CoreWCF

Frequently Asked Questions

What is CVE-2026-54776?
CVE-2026-54776 is a security vulnerability in CoreWCF involving Unix Domain Socket PosixIdentity transport accepts connections that skip the security upgrade under CWE-306: Missing Authentication for Critical Function.
Which CoreWCF versions are affected?
Affected versions include releases prior to 1.8.1, 1.9.1 across affected packages: CoreWCF.UnixDomainSocket.
What version fixes CVE-2026-54776?
Upgrading to 1.8.1, 1.9.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is CoreWCF.UnixDomainSocket affected?
Yes, CoreWCF.UnixDomainSocket 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-2026-54776?
CVE-2026-54776 has a CVSS v3.1 base score of 4.4 (MODERATE) with vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N.
What CWE is associated with CVE-2026-54776?
CVE-2026-54776 is classified under CWE-306: Missing Authentication for Critical Function (The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.).
How can I check NuGet dependencies for CVE-2026-54776?
Run the dependency tree command: 'inspect dependencies for CoreWCF.UnixDomainSocket'. 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-wjpq-6766-7f5j",
  "modified" : "2026-06-19T20:46:52Z",
  "published" : "2026-06-19T20:46:52Z",
  "aliases" : [ "CVE-2026-54776" ],
  "summary" : "CoreWCF: Unix Domain Socket PosixIdentity transport accepts connections that skip the security upgrade",
  "details" : "### Impact\nA CoreWCF service hosted on Unix Domain Sockets with the PosixIdentity client credential type (UnixDomainSocketBinding with Security.Mode = TransportCredentialOnly and Security.Transport.ClientCredentialType = PosixIdentity) does not require the client to perform the application/unixposix stream upgrade before dispatching messages.\n\n### Patches\nFixed in CoreWCF v1.8.1 and v1.9.1\n\n### Workarounds\nRestrict filesystem access to the UDS socket file using owner/group/mode (e.g. chmod 0660 plus a dedicated group) so that only the POSIX users who are already authorized to invoke the service can connect at all. This makes the missing-upgrade behaviour equivalent to the operating system’s filesystem permissions instead of relying on framing-layer identity checks.\nAvoid relying on ServiceSecurityContext.PrimaryIdentity for authorization decisions, or back it up with an authentication-required authorization policy that rejects anonymous principals.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "CoreWCF.UnixDomainSocket"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.8.1"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "CoreWCF.UnixDomainSocket"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.9.0"
      }, {
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      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/CoreWCF/CoreWCF/security/advisories/GHSA-wjpq-6766-7f5j"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/CoreWCF/CoreWCF"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-306" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-19T20:46:52Z",
    "nvd_published_at" : null
  }
}