CVE-2023-32615: TALOS-2023-1771 || Cisco Talos Intelligence Group

SUMMARY

A file write vulnerability exists in the OAS Engine configuration functionality of Open Automation Software OAS Platform v18.00.0072. A specially crafted series of network requests can lead to arbitrary file creation or overwrite. An attacker can send a sequence of requests to trigger this vulnerability.

CONFIRMED VULNERABLE VERSIONS

The versions below were either tested or verified to be vulnerable by Talos or confirmed to be vulnerable by the vendor.

Open Automation Software OAS Platform v18.00.0072

PRODUCT URLS

OAS Platform - https://openautomationsoftware.com/knowledge-base/getting-started-with-oas/

CVSSv3 SCORE

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

CWE

CWE-73 - External Control of File Name or Path

DETAILS

The OAS Platform, capable of running on a variety of systems including Windows, Linux, and Docker, was built to facilitate simplified communication between various proprietary devices and applications that might otherwise be incompatible. This is done through use of the “Universal Data Connector”. In the “Connectivity Layer” OAS acts as an “IoT Gateway and protocol bus,” allowing for native communication with devices, databases, and cloud services. Connectors implemented in the “Connectivity Layer” can then communicate with each other via the OAS Live Data Cloud, representing the “Aggregation Layer”. This information can then be stored, analyzed, and visualized through the data historian, alarm logging/notification, and visualization tools that make up the “Application Layer”. OAS additionally exposes a few sets of developer tools, allowing for programmatic access to the platform.

The OAS configuration tool provides a feature to save the running configuration to disk on the OAS engine server. When this information gets saved, the user specifies both the path and filename, restricted only by the permissions of the underlying OAS user system account. If the chosen file already exists, the contents of that file will be replaced with the configuration data.

To overwrite a file, a String protobuf, can be leveraged as part of a greater authenticated request to specify the filename. The format of this structure resembles the following, where the String field contains the absolute path to the target file:

message String {
  int32 Version = 1;
  U_EP UEP = 2;
  string String = 3;
}

Configuration data cannot be directly controlled, but it is possible to affect a subset of the data by strategically creating elements within the application, such as creating a new user.

When combined with one of the authentication bypass vulnerabilities and the user creation functionality, it is possible to gain access to the underlying system by overwriting the OAS user’s authorized_keys file with an attacker-controlled SSH key.

Mitigation

Access to the OAS Engine configuration server and its traffic should be restricted to exclusively those hosts authorized for configuration. Additionally, where possible, restrict read/write access for the OAS user to only locations that can safely be exposed to anyone on the network.

VENDOR RESPONSE

The fixed version v19 can be downloaded from: https://openautomationsoftware.com/downloads/releases/

TIMELINE

2023-06-22 - Vendor Disclosure
2023-09-02 - Vendor Patch Release
2023-09-05 - Public Release

Discovered by a member of Cisco Talos.