CoreWCF: Authentication bypass in CoreWCF SAML 1.1 / 2.0 token signature validation

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

10.0 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N

EPSS

• CVE-2026-54782: 0.41% estimated exploitation activity in the next 30 days; percentile 35.79 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact Full impersonation of any principal the trusted STS could have issued an assertion for — including administrative principals when the relying party grants them via SAML claims. Affects both SAML 1.1 and SAML 2.0. Preconditions Relying-party service is hosted with WSFederationHttpBinding or WS2007FederationHttpBinding (or any binding that triggers FederatedSecurityTokenManager for issued-token validation), and IdentityConfiguration is wired (UseIdentityConfiguration = true). Attacker can reach the service over the network and knows the trusted STS’s public certificate (public certs are by design discoverable). Patches Fixed in CoreWCF v1.8.1 and v1.9.1 Workarounds None

Published by the source

19 Jun 2026, 20:47 UTC

Last modified by the source

19 Jun 2026, 20:47 UTC

Source last checked

26 Oct 2026, 17:04 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-xjr9-gg9q-jx3v

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# Patch Next advisory brief: CVE-2026-54782

Advisory: CoreWCF: Authentication bypass in CoreWCF SAML 1.1 / 2.0 token signature validation
IDs: CVE-2026-54782, GHSA-xjr9-gg9q-jx3v
Record: https://patchnext.com/advisories/cve-2026-54782 (revision 1, source checked 26 Oct 2026, 17:04 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 10.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: corewcf.primitives 1.9.1, 1.8.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet corewcf.primitives: affected < 1.8.1; >= 1.9.0, < 1.9.1; fixed in 1.8.1, 1.9.1

## Suggested inspection (read-only)
- NuGet corewcf.primitives: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on corewcf.primitives.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-xjr9-gg9q-jx3v (GitHub-reviewed advisory GHSA-xjr9-gg9q-jx3v lists affected ranges: NuGet corewcf.primitives >=0 =1.9.0 <1.9.1)

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