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Vulnerability record · CVE-2021-25641 · published 1 June 2021

CVE-2021-25641: Apache dubbo deserialization of untrusted data vulnerability

Apache · Dubbo

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.

9.8 CVSS 3.1 Critical EPSS 21% · top 2.5% CWE-502 · Deserialization of untrusted data
9.8CVSS 3.1 base score, v2 7.5
21%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References
17 Jun 2026Last modified by NVD

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:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://lists.apache.org/thread.html/r99ef7fa35585d3a68762de07e8d2b2bc48b8fa669a03e8d84b9673f3%40%3Cdev.dubbo.apache.org Mailing ListVendor Advisory
https://lists.apache.org/thread.html/r99ef7fa35585d3a68762de07e8d2b2bc48b8fa669a03e8d84b9673f3%40%3Cdev.dubbo.apache.org Mailing ListVendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2021-25641), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.