---
title: "CVE-2026-54782: CoreWCF: Authentication bypass in CoreWCF SAML 1.1 / 2.0 token signature validation"
url: https://erroneo.us/security/cve/CVE-2026-54782/
description: "CVE-2026-54782 (CoreWCF.Primitives (NuGet)): CoreWCF is a port of the service side of Windows Communication Foundation (WCF) to .NET Core. Prior to 1.8.1…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-07-08
date_modified: 2026-07-10
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-54782"
kev: false
cvss: 10
epss: 0.00414
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-54782: CoreWCF: Authentication bypass in CoreWCF SAML 1.1 / 2.0 token signature validation

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.4% , percentile 35: FIRST’s model estimates a 0.4% chance of exploitation activity in the next 30 days, higher than 35% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes CoreWCF.Primitives (NuGet) < 1.8.1, fixed in 1.8.1 ; CoreWCF.Primitives (NuGet) >= 1.9.0, < 1.9.1, fixed in 1.9.1 . Check your lockfile, including transitive dependencies.

## What it is

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 SAML 1.1 and SAML 2.0 token validation does not correctly resolve the issuer signing key or require signed tokens when IdentityConfiguration is used with federated bindings, allowing an unauthenticated remote attacker to impersonate any principal the trusted STS could issue. This issue is fixed in versions 1.8.1 and 1.9.1.

## Affected packages

- NuGet `CoreWCF.Primitives` < 1.8.1 → fixed: 1.8.1
- NuGet `CoreWCF.Primitives` >= 1.9.0, < 1.9.1 → fixed: 1.9.1

## Affected products (CVE record)

- CoreWCF CoreWCF: >= 1.9.0, < 1.9.1, < 1.8.1

## Severity

- GitHub_M CVSS 3.1: 10 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N`
- GitHub CVSS 3.1: 10.0 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.41% probability of exploitation activity in the next 30 days; percentile 35.

## Sources

- [GitHub Advisory GHSA-xjr9-gg9q-jx3v](https://github.com/advisories/GHSA-xjr9-gg9q-jx3v)
- [CVE.org record CVE-2026-54782](https://www.cve.org/CVERecord?id=CVE-2026-54782)
- [NVD entry CVE-2026-54782](https://nvd.nist.gov/vuln/detail/CVE-2026-54782)
- [github.com](https://github.com/CoreWCF/CoreWCF/security/advisories/GHSA-xjr9-gg9q-jx3v)
- [github.com](https://github.com/CoreWCF/CoreWCF/commit/0b8c8af851260e85e8402af53233d1b8f87dfb6f)
- [github.com](https://github.com/CoreWCF/CoreWCF/commit/0e63c2cca55763d8be6b226a234579280a09e7b6)
- [github.com](https://github.com/CoreWCF/CoreWCF/commit/e5cc9b6a4ecc102a50d782093bfc72e0790abe3d)
- [github.com](https://github.com/CoreWCF/CoreWCF/releases/tag/v1.8.1)
- [github.com](https://github.com/CoreWCF/CoreWCF/releases/tag/v1.9.1)

---
Source page: https://erroneo.us/security/cve/CVE-2026-54782/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt