# CVE-2026-54783 — CoreWCF

> As of 2026-07-10, CVE-2026-54783 is a HIGH-severity vulnerability in CoreWCF, CVSS v3.1 7.4, EPSS 0.1% (3.9th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-54783 as of 2026-07-10; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-07-10

## What is CVE-2026-54783?

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, CoreWCF WS-Security endorsing and supporting signature verification does not ensure the selected ds:Signature covers the expected Security header target, allowing an attacker with one captured signed SOAP envelope to replay arbitrary service operations as the victim principal. This issue is fixed in versions 1.8.1 and 1.9.1.

The record classifies CVE-2026-54783 under weakness classes [CWE-294](https://intel.threadlinqs.com/cwe/CWE-294), [CWE-345](https://intel.threadlinqs.com/cwe/CWE-345), [CWE-347](https://intel.threadlinqs.com/cwe/CWE-347). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity. 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:** 7.4 — HIGH (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **EPSS (FIRST):** 0.1% probability of exploitation in the next 30 days, higher than 3.9% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 3.9/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-07-08, last modified 2026-07-10

## Is CVE-2026-54783 being exploited?

It currently carries a trending score of 30 in the Threadlinqs vulnerability feed.

## Affected products and versions

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

Affected software packages:

- `nuget:CoreWCF.Primitives` — patched in 1.8.1
- `nuget:CoreWCF.Primitives` — patched in 1.9.1

## How to fix CVE-2026-54783

Fixed versions are recorded for 2 packages: nuget:CoreWCF.Primitives 1.8.1, nuget:CoreWCF.Primitives 1.9.1. No vendor patch reference has been recorded for CVE-2026-54783 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-2026-54783

No threat campaign in the Threadlinqs corpus currently references CVE-2026-54783, 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, GitHub Security Advisories. 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-gqv6-pwcg-87r8)

**Other references**

- [github.com](https://github.com/CoreWCF/CoreWCF/commit/0589692d4b9a41d21b34ac48281e95f6df7f4ce5)
- [github.com (30aef805270976c42477e3f2a05f4e563d86e247)](https://github.com/CoreWCF/CoreWCF/commit/30aef805270976c42477e3f2a05f4e563d86e247)
- [github.com (4618f24165ad018ad3ed2636bf8c3bc87d2a3be2)](https://github.com/CoreWCF/CoreWCF/commit/4618f24165ad018ad3ed2636bf8c3bc87d2a3be2)
- [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-2026-54783
Full detection coverage and IOCs for threats exploiting CVE-2026-54783 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp