Apache Software Foundation · Apache Tapestry
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.
First seen exploited 3 years after disclosure. Public exploit code (Metasploit) was available the same day.
A fix was bypassed or incomplete once over 19 months. The latest fix listed for tapestry-core is 5.8.2.
Why these are linked: Link confidenceHow strong the evidence is that two CVEs are related. High: stated in the CVE text or linked in an advisory, or the same code was patched one release apart. Medium: the same code, or a version step plus a similar description. Low: similar description only.
The vulnerability I have found is a bypass of the fix for CVE-2019-0195.
No ATT&CK techniques are linked to this CVE yet. MITRE CTID has not mapped it, and no report passage in the corpus ties it to a technique.
1 package in 1 ecosystem. Main package: org.apache.tapestry:tapestry-core.
Upgrade to 5.7.1 or later
Set the version to 5.7.1 or later in your pom.xml or build.gradle.
The first fix for CVE-2021-27850. No other CVE tracked by Patchfirst affects this package.
| If you run | Upgrade to |
|---|---|
| 5.7.0 up to 5.7.1 | 5.7.1 |
| 5.4.0 up to 5.6.3 | 5.6.3 |
“Up to” means the second version is the fix and is not affected.