CVE-2021-27850

{"cve": {"data_type": "CVE", "references": {"reference_data": [{"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", "tags": ["Mailing List", "Vendor Advisory"], "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": ["Exploit", "Mailing List", "Third Party Advisory"], "refsource": "MLIST"}, {"url": "https://security.netapp.com/advisory/ntap-20210528-0002/", "name": "https://security.netapp.com/advisory/ntap-20210528-0002/", "tags": ["Third Party Advisory"], "refsource": "CONFIRM"}]}, "data_format": "MITRE", "description": {"description_data": [{"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."}]}, "problemtype": {"problemtype_data": [{"description": [{"lang": "en", "value": "CWE-502"}]}]}, "data_version": "4.0", "CVE_data_meta": {"ID": "CVE-2021-27850", "ASSIGNER": "security@apache.org"}}, "impact": {"baseMetricV2": {"cvssV2": {"version": "2.0", "baseScore": 10.0, "accessVector": "NETWORK", "vectorString": "AV:N/AC:L/Au:N/C:C/I:C/A:C", "authentication": "NONE", "integrityImpact": "COMPLETE", "accessComplexity": "LOW", "availabilityImpact": "COMPLETE", "confidentialityImpact": "COMPLETE"}, "severity": "HIGH", "acInsufInfo": false, "impactScore": 10.0, "obtainAllPrivilege": false, "exploitabilityScore": 10.0, "obtainUserPrivilege": false, "obtainOtherPrivilege": false, "userInteractionRequired": false}, "baseMetricV3": {"cvssV3": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 9.8, "attackVector": "NETWORK", "baseSeverity": "CRITICAL", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "integrityImpact": "HIGH", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "NONE", "confidentialityImpact": "HIGH"}, "impactScore": 5.9, "exploitabilityScore": 3.9}}, "publishedDate": "2021-04-15T08:15Z", "configurations": {"nodes": [{"children": [], "operator": "OR", "cpe_match": [{"cpe23Uri": "cpe:2.3:a:apache:tapestry:*:*:*:*:*:*:*:*", "cpe_name": [], "vulnerable": true, "versionEndExcluding": "5.6.2", "versionStartIncluding": "5.4.0"}, {"cpe23Uri": "cpe:2.3:a:apache:tapestry:*:*:*:*:*:*:*:*", "cpe_name": [], "vulnerable": true, "versionEndExcluding": "5.7.1", "versionStartIncluding": "5.7.0"}]}], "CVE_data_version": "4.0"}, "lastModifiedDate": "2021-06-02T15:15Z"}