Hyland PACSgear MediaWriter 5.2.1 MediaWriter Service PacsgearMediaServerEngine.dll WebClient missing authentication

Summaryinfo

A vulnerability was found in Hyland PACSgear MediaWriter 5.2.1. It has been classified as critical. Impacted is the function WebClient in the library PacsgearMediaServerEngine.dll of the component MediaWriter Service. The manipulation leads to missing authentication. This vulnerability is documented as CVE-2026-58127. The attack can be initiated remotely. There is not any exploit available.

Detailsinfo

A vulnerability was found in Hyland PACSgear MediaWriter 5.2.1 and classified as critical. This issue affects the function WebClient in the library PacsgearMediaServerEngine.dll of the component MediaWriter Service. The manipulation with an unknown input leads to a missing authentication vulnerability. Using CWE to declare the problem leads to CWE-306. The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

PACSgear MediaWriter 5.2.1 exposes a .NET Remoting TCP service on port 9000 via PacsgearMediaServerEngine.dll, registered with ObjectURIs RemoteObj and UIRemoteObj, without any authentication requirement. By exploiting the MarshalByRefObject object unmarshalling technique and implementing .NET WebClient class methods, an unauthenticated remote attacker can read and write arbitrary files on the host filesystem. The ObjectURIs are identical across all installations by default. Chaining the arbitrary file write primitive with DLL hijacking opportunities in the MediaWriter service (which runs as NT Authority\\SYSTEM and loads missing DLLs such as CRYPTBASE.DLL from the application directory) enables unauthenticated remote code execution as SYSTEM upon service restart.

The weakness was released by Victor A. Morales. It is possible to read the advisory at gist.github.com. The identification of this vulnerability is CVE-2026-58127 since 06/29/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 07/01/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Vendor

• Hyland

Name

• PACSgear MediaWriter

Version

• 5.2.1

CPE 2.3info

• 🔒

CPE 2.2info

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