# CVE-2026-54783: CoreWCF: XML Signature Wrapping in WS-Security endorsing/supporting signature verification allows replay of captured signed messages

> Attackers can replay captured signed SOAP messages to execute arbitrary service operations as the victim due to improper signature verification in CoreWCF.

- **Severity:** High 7.4 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 8 Jul 2026
- **Updated:** 10 Jul 2026
- **Also known as:** GHSA-gqv6-pwcg-87r8

## What is CVE-2026-54783?

CVE-2026-54783 is a high-severity authentication bypass vulnerability in CoreWCF, published on 8 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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, 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.

Weakness: CWE-347 (Improper Verification of Cryptographic Signature), CWE-345 (Insufficient Verification of Data Authenticity), CWE-294 (Authentication Bypass by Capture-replay)

## Which versions are affected by CVE-2026-54783?

4 open source packages ship an affected version, including CoreWCF.Primitives.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `CoreWCF.Primitives` | NuGet | All versions | 1.8.1 |
| `CoreWCF.Primitives` | NuGet | All versions | 1.8.1 |
| `CoreWCF.Primitives` | NuGet | From 1.9.0 | 1.9.1 |
| `CoreWCF.Primitives` | NuGet | From 1.9.0 | 1.9.1 |

## How do I fix CVE-2026-54783?

Upgrade CoreWCF.Primitives to a fixed version for your release line: 1.8.1 or 1.9.1.

## Is CVE-2026-54783 being exploited?

There is no known exploitation of CVE-2026-54783 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-54783 and fix it if it is affected.

What it is: CVE-2026-54783 is a high-severity authentication bypass vulnerability in CoreWCF, published on 8 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-54783 in the wild and no public exploit code.

Affected packages and fixed versions:
- CoreWCF.Primitives (NuGet): affected all versions; fixed in 1.8.1
- CoreWCF.Primitives (NuGet): affected all versions; fixed in 1.8.1
- CoreWCF.Primitives (NuGet): affected from 1.9.0; fixed in 1.9.1
- CoreWCF.Primitives (NuGet): affected from 1.9.0; fixed in 1.9.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-54783/ (Markdown: https://insights.sbomify.com/CVE-2026-54783/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-54783
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-54783
- OSV: https://osv.dev/vulnerability/CVE-2026-54783

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-54783/
Summaries are generated and may contain mistakes; the official description above is the record.