CVE-2021-27850
Summary
| CVE | CVE-2021-27850 |
|---|---|
| State | PUBLIC |
| Assigner | [email protected] |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2021-04-15 08:15:00 UTC |
| Updated | 2021-06-02 15:15:00 UTC |
| Description | 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. |
Risk And Classification
Problem Types: CWE-502
NVD Known Affected Configurations (CPE 2.3)
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| CVE-2021-27850 Apache Tapestry Vulnerability in NetApp Products | NetApp Product Security | CONFIRM | security.netapp.com | |
| Pony Mail! | MISC | lists.apache.org | |
| oss-security - CVE-2021-27850: Apache Tapestry: Bypass of the fix for CVE-2019-0195 | MLIST | www.openwall.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
LEGACY: Apache Tapestry would like to thank Johannes Moritz for finding and notifying this vulnerability