The code which checks HMAC in form submissions used String.equals() for comparisons, which results in a timing side channel for the comparison of the HMAC signatures. This could lead to remote code execution if an attacker is able to determine the correct signature for their payload. The comparison should be done with a constant time algorithm instead.

Manipulating classpath asset file URLs, an attacker could guess the path to a known file in the classpath and have it downloaded. If the attacker found the file with the value of the tapestry.hmac-passphrase configuration symbol, most probably the webapp's AppModule class, the value of this symbol could be used to craft a Java deserialization attack, thus running malicious injected Java code. The vector would be the t:formdata parameter from the Form component.

Tapestry processes assets /assets/ctx using classes chain StaticFilesFilter -> AssetDispatcher -> ContextResource, which doesn't filter the character \, so attacker can perform a path traversal attack to read any files on Windows platform.

In Apache Tapestry from 5.4.0 to 5.5.0, crafting specific URLs, an attacker can download files inside the WEB-INF folder of the WAR being run.

Information Exposure vulnerability in context asset handling of Apache Tapestry allows an attacker to download files inside WEB-INF if using a specially-constructed URL. This was caused by an incomplete fix for CVE-2020-13953. This issue affects Apache Tapestry Apache Tapestry 5.4.0 version to Apache Tapestry 5.6.3; Apache Tapestry 5.7.0 version and Apache Tapestry 5.7.1.

A critical unauthenticated remote code execution vulnerability was found all recent versions of Apache Tapestry. The affected versions include 5.4.5, 5.5.0, 5.6.2 and 5.7.0. The vulnerability I have found is a bypass of the fix for CVE-2019-0195. Recap: Before the fix of CVE-2019-0195 it was possible to download arbitrary class files from the classpath by providing a crafted asset file URL. An attacker was able to download the file AppModule.class by requesting the URL http://localhost:8080/assets/something/services/AppModule.class which contains a HMAC secret key. The fix for that bug was a blacklist filter that checks if the URL ends with .class, .properties or .xml. Bypass: Unfortunately, the blacklist solution can simply be bypassed by appending a / at the end of the URL: http://localhost:8080/assets/something/services/AppModule.class/ The slash is stripped after the blacklist check and the file AppModule.class is loaded into the response. This class usually contains the HMAC secret key which is used to sign serialized Java objects. With the knowledge of that key an attacker can sign a Java gadget chain that leads to RCE (e.g. CommonsBeanUtils1 from ysoserial). Solution for this vulnerability: For Apache Tapestry 5.4.0 to 5.6.1, upgrade to 5.6.2 or later. For Apache Tapestry 5.7.0, upgrade to 5.7.1 or later.