{"api_version":"1","generated_at":"2026-04-25T15:33:06+00:00","cve":"CVE-2021-27850","urls":{"html":"https://cve.report/CVE-2021-27850","api":"https://cve.report/api/cve/CVE-2021-27850.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2021-27850","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-27850"},"summary":{"title":"CVE-2021-27850","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.","state":"PUBLIC","assigner":"security@apache.org","published_at":"2021-04-15 08:15:00","updated_at":"2021-06-02 15:15:00"},"problem_types":["CWE-502"],"metrics":[],"references":[{"url":"https://security.netapp.com/advisory/ntap-20210528-0002/","name":"https://security.netapp.com/advisory/ntap-20210528-0002/","refsource":"CONFIRM","tags":[],"title":"CVE-2021-27850 Apache Tapestry Vulnerability in NetApp Products | NetApp Product Security","mime":"text/html","httpstatus":"200","archivestatus":"404"},{"url":"https://lists.apache.org/thread.html/r237ff7f286bda31682c254550c1ebf92b0ec61329b32fbeb2d1c8751%40%3Cusers.tapestry.apache.org%3E","name":"https://lists.apache.org/thread.html/r237ff7f286bda31682c254550c1ebf92b0ec61329b32fbeb2d1c8751%40%3Cusers.tapestry.apache.org%3E","refsource":"MISC","tags":[],"title":"Pony Mail!","mime":"text/html","httpstatus":"200","archivestatus":"200"},{"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","refsource":"MLIST","tags":[],"title":"oss-security - CVE-2021-27850: Apache Tapestry: Bypass of the fix for CVE-2019-0195","mime":"text/html","httpstatus":"200","archivestatus":"404"},{"url":"https://www.cve.org/CVERecord?id=CVE-2021-27850","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-27850","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[{"source":"LEGACY","value":"Apache Tapestry would like to thank Johannes Moritz for finding and notifying this vulnerability","lang":""}],"nvd_cpes":[{"cve_year":"2021","cve_id":"27850","vulnerable":"1","versionEndIncluding":"","cpe1":"cpe","cpe2":"2.3","cpe3":"a","cpe4":"apache","cpe5":"tapestry","cpe6":"*","cpe7":"*","cpe8":"*","cpe9":"*","cpe10":"*","cpe11":"*","cpe12":"*","cpe13":"*"}],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[{"cve":"CVE-2021-27850","qid":"730165","title":"Apache Tapestry Remote Code Execution Vulnerability Detected"},{"cve":"CVE-2021-27850","qid":"982236","title":"Java (maven) Security Update for org.apache.tapestry:tapestry-core (GHSA-mj8x-cpr8-x39h)"}]},"source_records":{"cve_program":{"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":[{"refsource":"MISC","url":"https://lists.apache.org/thread.html/r237ff7f286bda31682c254550c1ebf92b0ec61329b32fbeb2d1c8751%40%3Cusers.tapestry.apache.org%3E","name":"https://lists.apache.org/thread.html/r237ff7f286bda31682c254550c1ebf92b0ec61329b32fbeb2d1c8751%40%3Cusers.tapestry.apache.org%3E"},{"refsource":"MLIST","name":"[oss-security] 20210414 CVE-2021-27850: Apache Tapestry: Bypass of the fix for CVE-2019-0195","url":"http://www.openwall.com/lists/oss-security/2021/04/15/1"},{"refsource":"CONFIRM","name":"https://security.netapp.com/advisory/ntap-20210528-0002/","url":"https://security.netapp.com/advisory/ntap-20210528-0002/"}]},"source":{"defect":["TAP5-2663"],"discovery":"UNKNOWN"}},"nvd":{"publishedDate":"2021-04-15 08:15:00","lastModifiedDate":"2021-06-02 15:15:00","problem_types":["CWE-502"],"metrics":{"baseMetricV3":{"cvssV3":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH","baseScore":9.8,"baseSeverity":"CRITICAL"},"exploitabilityScore":3.9,"impactScore":5.9},"baseMetricV2":{"cvssV2":{"version":"2.0","vectorString":"AV:N/AC:L/Au:N/C:C/I:C/A:C","accessVector":"NETWORK","accessComplexity":"LOW","authentication":"NONE","confidentialityImpact":"COMPLETE","integrityImpact":"COMPLETE","availabilityImpact":"COMPLETE","baseScore":10},"severity":"HIGH","exploitabilityScore":10,"impactScore":10,"acInsufInfo":false,"obtainAllPrivilege":false,"obtainUserPrivilege":false,"obtainOtherPrivilege":false,"userInteractionRequired":false}},"configurations":{"CVE_data_version":"4.0","nodes":[{"operator":"OR","children":[],"cpe_match":[{"vulnerable":true,"cpe23Uri":"cpe:2.3:a:apache:tapestry:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7.0","versionEndExcluding":"5.7.1","cpe_name":[]},{"vulnerable":true,"cpe23Uri":"cpe:2.3:a:apache:tapestry:*:*:*:*:*:*:*:*","versionStartIncluding":"5.4.0","versionEndExcluding":"5.6.2","cpe_name":[]}]}]}},"legacy_mitre":{"record":{"CveYear":"2021","CveId":"27850","Ordinal":"202962","Title":"CVE-2021-27850","CVE":"CVE-2021-27850","Year":"2021"},"notes":[{"CveYear":"2021","CveId":"27850","Ordinal":"1","NoteData":"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.","Type":"Description","Title":null},{"CveYear":"2021","CveId":"27850","Ordinal":"2","NoteData":"2021-04-15","Type":"Other","Title":"Published"},{"CveYear":"2021","CveId":"27850","Ordinal":"3","NoteData":"2021-05-28","Type":"Other","Title":"Modified"}]}}}