Gradle is a build tool with a focus on build automation and support for multi-language development. In some cases, when Gradle parses XML files, resolving XML external entities is not disabled. Combined with an Out Of Band XXE attack (OOB-XXE), just parsing XML can lead to exfiltration of local text files to a remote server. Gradle parses XML files for several purposes. Most of the time, Gradle parses XML files it generated or were already present locally. Only Ivy XML descriptors and Maven POM files can be fetched from remote repositories and parsed by Gradle. In Gradle 7.6.3 and 8.4, resolving XML external entities has been disabled for all use cases to protect against this vulnerability. Gradle will now refuse to parse XML files that have XML external entities.
The product processes an XML document that can contain XML entities with URIs that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Gradle | Gradle | * | 7.6.3 (excluding) |
| Gradle | Gradle | 8.0.0 (including) | 8.4.0 (excluding) |
| Red Hat AMQ Streams 2.6.0 | RedHat | gradle | * |
| Gradle | Ubuntu | bionic | * |
| Gradle | Ubuntu | lunar | * |
| Gradle | Ubuntu | mantic | * |
| Gradle | Ubuntu | trusty | * |
| Gradle | Ubuntu | xenial | * |
XML documents optionally contain a Document Type Definition (DTD), which, among other features, enables the definition of XML entities. It is possible to define an entity by providing a substitution string in the form of a URI. The XML parser can access the contents of this URI and embed these contents back into the XML document for further processing. By submitting an XML file that defines an external entity with a file:// URI, an attacker can cause the processing application to read the contents of a local file. For example, a URI such as “file:///c:/winnt/win.ini” designates (in Windows) the file C:\Winnt\win.ini, or file:///etc/passwd designates the password file in Unix-based systems. Using URIs with other schemes such as http://, the attacker can force the application to make outgoing requests to servers that the attacker cannot reach directly, which can be used to bypass firewall restrictions or hide the source of attacks such as port scanning. Once the content of the URI is read, it is fed back into the application that is processing the XML. This application may echo back the data (e.g. in an error message), thereby exposing the file contents.