CoreWCF NetNamedPipe transport accepts attach to a pre-existing named pipe instance

Exploitation

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

CVSS

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

EPSS

• CVE-2026-54777: 0.12% estimated exploitation activity in the next 30 days; percentile 1.65 (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 CoreWCF NetNamedPipe transport accepts attach to a pre-existing named pipe instance, allowing local interception of NetNamedPipe traffic. NetNamedPipe creates a shared memory object based on the listening url, then generated a unique GUID for the named pipe it will be using and saves this to the shared memory object. Then it creates the named pipe to listen for clients. This requires an attacker to race the service and create the named pipe between the service publishing the GUID to the shared memory location (which the attacker needs to read) and the service creating the named pipe itself. Patches Fixed in CoreWCF v1.8.1 and v1.9.1 Workarounds None

Published by the source

19 Jun 2026, 20:46 UTC

Last modified by the source

19 Jun 2026, 20:46 UTC

Source last checked

26 Oct 2026, 17:04 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-6jj2-4q5c-x8g6

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# Patch Next advisory brief: CVE-2026-54777

Advisory: CoreWCF NetNamedPipe transport accepts attach to a pre-existing named pipe instance
IDs: CVE-2026-54777, GHSA-6jj2-4q5c-x8g6
Record: https://patchnext.com/advisories/cve-2026-54777 (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: Medium (CVSS 6.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: corewcf.netnamedpipe 1.9.1, 1.8.1. A vendor fix does not mean a deployment is fixed.

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

## Suggested inspection (read-only)
- NuGet corewcf.netnamedpipe: 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.netnamedpipe.
- 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-6jj2-4q5c-x8g6 (GitHub-reviewed advisory GHSA-6jj2-4q5c-x8g6 lists affected ranges: NuGet corewcf.netnamedpipe >=0 =1.9.0 <1.9.1)

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