# CVE-2026-54783: CoreWCF signature verification bypass in WS-Security

Source: https://junglewise.ai/threats/cve-2026-54783-corewcf-signature-verification-bypass-in-ws-security  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-08. Updated: 2026-07-08  
License: CC BY 4.0 with a link back

CVE-2026-54783 · Severity: high · CVSS 7.4 · Published 2026-07-08

CoreWCF is a tool used by developers to build web services on modern .NET platforms. A security flaw in its message verification system allows an attacker to capture a legitimate, signed message and reuse it to perform unauthorized actions as if they were the original user. This could lead to unauthorized data access or the execution of sensitive business operations without proper permission.

Technologies: [CoreWCF](https://junglewise.ai/threats/technologies/corewcf), [CoreWCF.Primitives (NuGet)](https://junglewise.ai/threats/technologies/corewcf-primitives). Vendors: [CoreWCF](https://junglewise.ai/threats/vendors/corewcf), [NuGet](https://junglewise.ai/threats/vendors/nuget).

## Quick answers

**Is CVE-2026-54783 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-54783 being exploited in the wild.

**How severe is CVE-2026-54783?** High severity, with a CVSS score of 7.4, published 8 July 2026.

**Which products and versions are affected?** CoreWCF < 1.8.1, >= 1.9.0 < 1.9.1; CoreWCF.Primitives (NuGet) ECOSYSTEM:introduced=0,fixed=1.8.1.

**Is there a fix for CVE-2026-54783?** Yes. CoreWCF.Primitives (NuGet): upgrade to 1.8.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-54783 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-54783?** Check whether you run CoreWCF or CoreWCF.Primitives (NuGet) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- CoreWCF.Primitives (NuGet): upgrade to 1.8.1 or later

  ```sh
  dotnet add package CoreWCF.Primitives --version 1.8.1
  ```


## Technical details

A vulnerability exists in CoreWCF's WS-Security implementation where endorsing and supporting signature verification does not properly validate that the 'ds:Signature' element covers the intended Security header target. Specifically, the 'ReadSignatureCore' and 'VerifySignatureAsync' functions failed to strictly bind signature lookups to the Security header subtree, allowing an attacker to 'steer' the receiver into validating a smuggled signature from a sibling header. By capturing a single signed SOAP envelope, a remote attacker can replay arbitrary service operations as the victim principal. The fix introduces 'FindSecurityHeaderSignatureElement' and 'EnsureSignatureCoversExpectedTarget' to enforce proper signature coverage.

## Affected products

- CoreWCF CoreWCF < 1.8.1, >= 1.9.0 < 1.9.1

## Identifiers

- CVE-2026-54783
- GHSA-gqv6-pwcg-87r8

## Timeline

- 2026-07-08: advisory: NVD publication date
- 2026-06-04: patched: Fix committed to repository

## References

- [https://github.com/CoreWCF/CoreWCF/commit/0589692d4b9a41d21b34ac48281e95f6df7f4ce5](https://github.com/CoreWCF/CoreWCF/commit/0589692d4b9a41d21b34ac48281e95f6df7f4ce5)
- [https://github.com/CoreWCF/CoreWCF/commit/30aef805270976c42477e3f2a05f4e563d86e247](https://github.com/CoreWCF/CoreWCF/commit/30aef805270976c42477e3f2a05f4e563d86e247)
- [https://github.com/CoreWCF/CoreWCF/commit/4618f24165ad018ad3ed2636bf8c3bc87d2a3be2](https://github.com/CoreWCF/CoreWCF/commit/4618f24165ad018ad3ed2636bf8c3bc87d2a3be2)
- [https://github.com/CoreWCF/CoreWCF/releases/tag/v1.8.1](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/releases/tag/v1.9.1)
- [https://github.com/CoreWCF/CoreWCF/security/advisories/GHSA-gqv6-pwcg-87r8](https://github.com/CoreWCF/CoreWCF/security/advisories/GHSA-gqv6-pwcg-87r8)

## Related threats

- [CoreWCF cleartext proof key exposure in SPNEGO negotiation](https://junglewise.ai/threats/cve-2026-54784-corewcf-cleartext-proof-key-exposure-in-spnego-negotiation)
- [CoreWCF authentication bypass in SAML token validation](https://junglewise.ai/threats/cve-2026-54782-corewcf-authentication-bypass-in-saml-token-validation)
- [CoreWCF improper authentication in SAML SamlSecurityTokenHandler](https://junglewise.ai/threats/cve-2026-54781-corewcf-improper-authentication-in-saml-samlsecuritytokenhandler)
- [CoreWCF algorithm downgrade in WS-Security receive pipeline](https://junglewise.ai/threats/cve-2026-54780-corewcf-algorithm-downgrade-in-ws-security-receive-pipeline)
- [CoreWCF SAML token replay protection bypass in DefaultTokenReplayCache](https://junglewise.ai/threats/cve-2026-54779-corewcf-saml-token-replay-protection-bypass-in)