CVE-2021-27850: Bypass of the fix for CVE-2019-0195
Apache Software Foundation · Apache Tapestry
Vendor fix available · Affected: Apache Software Foundation Apache Tapestry · Exploitation: check available, not yet exploited
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Higher than 99% of scored CVEs
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DescriptionCVE.org
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.
Affected products1
From the CVE record. A product or version that is not listed is unknown, not unaffected.
- Apache Software Foundation · Apache TapestryApache Tapestry 5.5.0; Apache Tapestry 5.7.0; from Apache Tapestry 5.4.5 before Apache Tapestry 5.4.0*; from Apache Tapestry 5.6.2 before Apache Tapestry 5.6.0*
On the Atlas
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- Exploitation
- Check available, not yet exploited. A public nuclei template can confirm it on a system you are authorised to test.
- CISA KEV
- Not listed
- Public check
- Apache Tapestry - Remote Code Execution · nuclei template in projectdiscovery/nuclei-templates
- Published
- April 2021
CoverageNo articles yet
No CyberSIXT article names CVE-2021-27850 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.