CVE-2026-54776: Missing Auth (CVSS 4.4)

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, a CoreWCF service hosted on Unix Domain Sockets with PosixIdentity client credentials can accept connections that skip the application/unixposix stream upgrade before dispatching messages, bypassing framing-layer identity checks in UnixPosixIdentitySecurityUpgradeProvider. This issue is fixed in versions 1.8.1 and 1.9.1.

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CVSS v3.1 Score

4.4

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

EPSS — Exploit Prediction

0.0011

Probability of exploitation

0.01%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-306 Missing Authentication

References

Other References

https://github.com/CoreWCF/CoreWCF/commit/994431268e3362c0cd126450fe2a135c202551f3 https://github.com/CoreWCF/CoreWCF/commit/9af16955e51a57348dafce0019e259a092ef7440 https://github.com/CoreWCF/CoreWCF/commit/f2f1a05927a88b8a75fa0582fa8ed75eb891e463 https://github.com/CoreWCF/CoreWCF/releases/tag/v1.8.1 https://github.com/CoreWCF/CoreWCF/releases/tag/v1.9.1 https://github.com/CoreWCF/CoreWCF/security/advisories/GHSA-wjpq-6766-7f5j

Frequently Asked Questions

What is CVE-2026-54776? +

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, a CoreWCF service hosted on Unix Domain Sockets with PosixIdentity client credentials can accept connections that skip the application/unixposix stream upgrade before dispatching messages, bypassing framing-layer identity checks in UnixPosixIdentitySecurityUpgradeProvider. This issue is fixed in versions 1.8.1 and 1.9.1. It has a CVSS v3.1 base score of 4.4 (MEDIUM).

How severe is CVE-2026-54776? +

CVE-2026-54776 has a CVSS v3.1 score of 4.4 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0011, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-54776? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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