{"cve":"CVE-2021-25641","nvd":{"published":"2021-06-01T14:15:09.737","modified":"2026-06-17T03:42:15.763","status":"Modified","description":"Each Apache Dubbo server will set a serialization id to tell the clients which serialization protocol it is working on. But for Dubbo versions before 2.7.8 or 2.6.9, an attacker can choose which serialization id the Provider will use by tampering with the byte preamble flags, aka, not following the server's instruction. This means that if a weak deserializer such as the Kryo and FST are somehow in code scope (e.g. if Kryo is somehow a part of a dependency), a remote unauthenticated attacker can tell the Provider to use the weak deserializer, and then proceed to exploit it.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","score":9.8},"cwes":["CWE-502"],"references":["https://lists.apache.org/thread.html/r99ef7fa35585d3a68762de07e8d2b2bc48b8fa669a03e8d84b9673f3%40%3Cdev.dubbo.apache.org%3E","https://lists.apache.org/thread.html/r99ef7fa35585d3a68762de07e8d2b2bc48b8fa669a03e8d84b9673f3%40%3Cdev.dubbo.apache.org%3E"],"products":["apache:dubbo"],"source":"nvd","synced_at":"2026-10-19T21:18:09.669877188+00:00"},"epss":{"cve":"CVE-2021-25641","score":0.21221,"percentile":0.97591,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-v2rg-8cwr-75g8","url":"https://osv.dev/vulnerability/GHSA-v2rg-8cwr-75g8","summary":"Deserializer tampering in Apache Dubbo","modified":"2023-11-08T04:05:15.584119Z","packages":[{"ecosystem":"Maven","name":"org.apache.dubbo:dubbo","purl":"pkg:maven/org.apache.dubbo/dubbo","ranges":[">=2.5.0 <2.7.8"],"fixed":["2.7.8"]},{"ecosystem":"Maven","name":"com.alibaba:dubbo","purl":"pkg:maven/com.alibaba/dubbo","ranges":[">=2.5.0 <2.6.9"],"fixed":["2.6.9"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}