{"id":"CVE-2021-27850","state":"PUBLISHED","title":"Bypass of the fix for CVE-2019-0195","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.","publishedAt":"2021-04-15T07:40:11.000Z","updatedAt":"2024-08-03T21:33:15.996Z","severity":null,"assigner":"apache","products":["Apache Software Foundation Apache Tapestry"],"affected":[{"vendor":"Apache Software Foundation","product":"Apache Tapestry","versions":[{"version":"Apache Tapestry 5.5.0","status":"affected"},{"version":"Apache Tapestry 5.7.0","status":"affected"},{"version":"Apache Tapestry 5.4.5","status":"affected","lessThan":"Apache Tapestry 5.4.0*","versionType":"custom"},{"version":"Apache Tapestry 5.6.2","status":"affected","lessThan":"Apache Tapestry 5.6.0*","versionType":"custom"}]}],"references":["https://lists.apache.org/thread.html/r237ff7f286bda31682c254550c1ebf92b0ec61329b32fbeb2d1c8751%40%3Cusers.tapestry.apache.org%3E","http://www.openwall.com/lists/oss-security/2021/04/15/1","https://security.netapp.com/advisory/ntap-20210528-0002/"],"weaknesses":["CWE-200","CWE-502"],"ingestedAt":"2026-10-29T19:48:15.637Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2021/27xxx/CVE-2021-27850.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.1","cveMetadata":{"cveId":"CVE-2021-27850","state":"PUBLISHED","datePublished":"2021-04-15T07:40:11.000Z","dateUpdated":"2024-08-03T21:33:15.996Z","assignerShortName":"apache","assignerOrgId":"f0158376-9dc2-43b6-827c-5f631a4d8d09","dateReserved":"2021-03-01T00:00:00.000Z"},"containers":{"cna":{"title":"Bypass of the fix for CVE-2019-0195","descriptions":[{"lang":"en","value":"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":[{"vendor":"Apache Software Foundation","product":"Apache Tapestry","versions":[{"version":"Apache Tapestry 5.5.0","status":"affected"},{"version":"Apache Tapestry 5.7.0","status":"affected"},{"version":"Apache Tapestry 5.4.5","status":"affected","lessThan":"Apache Tapestry 5.4.0*","versionType":"custom"},{"version":"Apache Tapestry 5.6.2","status":"affected","lessThan":"Apache Tapestry 5.6.0*","versionType":"custom"}]}],"references":[{"url":"https://lists.apache.org/thread.html/r237ff7f286bda31682c254550c1ebf92b0ec61329b32fbeb2d1c8751%40%3Cusers.tapestry.apache.org%3E","tags":["x_refsource_MISC"]},{"url":"http://www.openwall.com/lists/oss-security/2021/04/15/1","name":"[oss-security] 20210414 CVE-2021-27850: Apache Tapestry: Bypass of the fix for CVE-2019-0195","tags":["mailing-list","x_refsource_MLIST"]},{"url":"https://security.netapp.com/advisory/ntap-20210528-0002/","tags":["x_refsource_CONFIRM"]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-200","description":"CWE-200 Information Exposure","lang":"en","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-502","description":"CWE-502 Deserialization of Untrusted Data","lang":"en","type":"CWE"}]}],"providerMetadata":{"shortName":"apache","dateUpdated":"2021-05-28T09:06:12.000Z","orgId":"f0158376-9dc2-43b6-827c-5f631a4d8d09"},"credits":[{"lang":"en","value":"Apache Tapestry would like to thank Johannes Moritz for finding and notifying this vulnerability"}],"source":{"defect":["TAP5-2663"],"discovery":"UNKNOWN"},"x_generator":{"engine":"Vulnogram 0.0.9"},"x_legacyV4Record":{"CVE_data_meta":{"ASSIGNER":"security@apache.org","ID":"CVE-2021-27850","STATE":"PUBLIC","TITLE":"Bypass of the fix for CVE-2019-0195"},"affects":{"vendor":{"vendor_data":[{"product":{"product_data":[{"product_name":"Apache Tapestry","version":{"version_data":[{"version_affected":">=","version_name":"Apache Tapestry 5.4.0","version_value":"Apache Tapestry 5.4.5"},{"version_affected":"=","version_name":"Apache Tapestry 5.5.0","version_value":"Apache Tapestry 5.5.0"},{"version_affected":">=","version_name":"Apache Tapestry 5.6.0","version_value":"Apache Tapestry 5.6.2"},{"version_affected":"=","version_name":"Apache Tapestry 5.7.0","version_value":"Apache Tapestry 5.7.0"}]}}]},"vendor_name":"Apache Software Foundation"}]}},"credit":[{"lang":"eng","value":"Apache Tapestry would like to thank Johannes Moritz for finding and notifying this vulnerability"}],"data_format":"MITRE","data_type":"CVE","data_version":"4.0","description":{"description_data":[{"lang":"eng","value":"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."}]},"generator":{"engine":"Vulnogram 0.0.9"},"problemtype":{"problemtype_data":[{"description":[{"lang":"eng","value":"CWE-200 Information Exposure"}]},{"description":[{"lang":"eng","value":"CWE-502 Deserialization of Untrusted Data"}]}]},"references":{"reference_data":[{"name":"https://lists.apache.org/thread.html/r237ff7f286bda31682c254550c1ebf92b0ec61329b32fbeb2d1c8751%40%3Cusers.tapestry.apache.org%3E","refsource":"MISC","url":"https://lists.apache.org/thread.html/r237ff7f286bda31682c254550c1ebf92b0ec61329b32fbeb2d1c8751%40%3Cusers.tapestry.apache.org%3E"},{"name":"[oss-security] 20210414 CVE-2021-27850: Apache Tapestry: Bypass of the fix for CVE-2019-0195","refsource":"MLIST","url":"http://www.openwall.com/lists/oss-security/2021/04/15/1"},{"name":"https://security.netapp.com/advisory/ntap-20210528-0002/","refsource":"CONFIRM","url":"https://security.netapp.com/advisory/ntap-20210528-0002/"}]},"source":{"defect":["TAP5-2663"],"discovery":"UNKNOWN"}}},"adp":[{"title":"CVE Program Container","references":[{"url":"https://lists.apache.org/thread.html/r237ff7f286bda31682c254550c1ebf92b0ec61329b32fbeb2d1c8751%40%3Cusers.tapestry.apache.org%3E","tags":["x_refsource_MISC","x_transferred"]},{"url":"http://www.openwall.com/lists/oss-security/2021/04/15/1","name":"[oss-security] 20210414 CVE-2021-27850: Apache Tapestry: Bypass of the fix for CVE-2019-0195","tags":["mailing-list","x_refsource_MLIST","x_transferred"]},{"url":"https://security.netapp.com/advisory/ntap-20210528-0002/","tags":["x_refsource_CONFIRM","x_transferred"]}],"providerMetadata":{"shortName":"CVE","orgId":"af854a3a-2127-422b-91ae-364da2661108","dateUpdated":"2024-08-03T21:33:15.996Z"}}]}}}