# CVE-2026-54776 — CoreWCF

> As of 2026-07-09, CVE-2026-54776 is a MEDIUM-severity vulnerability in CoreWCF, CVSS v3.1 4.4, EPSS 0.1% (1.4th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-54776 as of 2026-07-09; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-07-09

## 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.

The record classifies CVE-2026-54776 under weakness class [CWE-306](https://intel.threadlinqs.com/cwe/CWE-306). Its CVSS v3 base vector states that the flaw requires local access to the host, needs low-privilege credentials, needs no user interaction. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 89 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 4.4 — MEDIUM (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N`)
- **EPSS (FIRST):** 0.1% probability of exploitation in the next 30 days, higher than 1.4% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 2.3/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-07-08, last modified 2026-07-09

## Is CVE-2026-54776 being exploited?

It currently carries a trending score of 29 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [CoreWCF](https://intel.threadlinqs.com/vendors/corewcf): CoreWCF

## How to fix CVE-2026-54776

No vendor patch reference has been recorded for CVE-2026-54776 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-54776

No threat campaign in the Threadlinqs corpus currently references CVE-2026-54776, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, NVD, FIRST EPSS. Last verified by Threadlinqs on 2026-07-12. This product uses the NVD API but is not endorsed or certified by the NVD.

**Vendor advisory and patch**

- [github.com](https://github.com/CoreWCF/CoreWCF/security/advisories/GHSA-wjpq-6766-7f5j)

**Other references**

- [github.com](https://github.com/CoreWCF/CoreWCF/commit/994431268e3362c0cd126450fe2a135c202551f3)
- [github.com (9af16955e51a57348dafce0019e259a092ef7440)](https://github.com/CoreWCF/CoreWCF/commit/9af16955e51a57348dafce0019e259a092ef7440)
- [github.com (f2f1a05927a88b8a75fa0582fa8ed75eb891e463)](https://github.com/CoreWCF/CoreWCF/commit/f2f1a05927a88b8a75fa0582fa8ed75eb891e463)
- [github.com (v1.8)](https://github.com/CoreWCF/CoreWCF/releases/tag/v1.8.1)
- [github.com (v1.9)](https://github.com/CoreWCF/CoreWCF/releases/tag/v1.9.1)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-54776
Full detection coverage and IOCs for threats exploiting CVE-2026-54776 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp