CVE-2021-25641: Dubbo Deserializer Tampering Vulnerability

CRITICAL
Advisory Identifier: GHSA-v2rg-8cwr-75g8
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CVSS 9.8
CWE-502
Published
Advisory Summary

CVE-2021-25641 is a CRITICAL (CVSS 9.8) deserializer tampering vulnerability (CWE-502: Deserialization of Untrusted Data) affecting Dubbo libraries in the Maven ecosystem. The issue involves deserializer tampering in apache dubbo. Remediation is available by upgrading affected packages to version 2.7.8, 2.6.9.

CVE-2021-25641 at a Glance

CVE Identifier CVE-2021-25641
GHSA Identifier GHSA-v2rg-8cwr-75g8
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-502: Deserialization of Untrusted Data
Affected Product Dubbo
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 9.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2021-25641

To remediate this vulnerability, upgrade all affected Dubbo dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

org.apache.dubbo:dubbo fixed: 2.7.8 
<dependency>
    <groupId>org.apache.dubbo</groupId>
    <artifactId>dubbo</artifactId>
    <version>2.7.8</version>
</dependency>
com.alibaba:dubbo fixed: 2.6.9 
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>dubbo</artifactId>
    <version>2.6.9</version>
</dependency>
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree -Dincludes=org.apache.dubbo

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2021-25641, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree -Dincludes=org.apache.dubbo

Analyze the terminal output to locate any version of Dubbo in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.7.8), your application is affected.

Note: The mvn dependency:tree -Dincludes=org.apache.dubbo command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-502: Deserialization of Untrusted Data, where the product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid. In Dubbo, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

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.

CVE-2021-25641 Affected Dubbo Versions

2 component(s)
Fixed Versions:
2.7.82.6.9
Product / Package Ecosystem Affected Versions Fixed Version
org.apache.dubbo:dubbo
maven/org.apache.dubbo/dubbo
Maven
≥ 2.5.0
< 2.7.8
2.7.8
com.alibaba:dubbo
maven/com.alibaba/dubbo
Maven
≥ 2.5.0
< 2.6.9
2.6.9

References

NVD — CVE-2021-25641 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-25641
lists.apache.org/thread.html/r99ef7f... WEB
https://lists.apache.org/thread.html/r99ef7fa35585d3a68762de07e8d2b2bc48b8fa669a03e8d84b9673f3%40%3Cdev.dubbo.apache.org%3E

Frequently Asked Questions

What is CVE-2021-25641?
CVE-2021-25641 is a security vulnerability in Dubbo involving Deserializer tampering in Apache Dubbo under CWE-502: Deserialization of Untrusted Data.
Which Dubbo versions are affected?
Affected versions include releases prior to 2.7.8, 2.6.9 across affected packages: org.apache.dubbo:dubbo, com.alibaba:dubbo.
What version fixes CVE-2021-25641?
Upgrading to 2.7.8, 2.6.9 (or the latest patched release for your respective branch) resolves the vulnerability.
Is dubbo affected?
Yes, org.apache.dubbo:dubbo is affected in releases prior to 2.7.8, 2.6.9. Upgrade your dependency to 2.7.8, 2.6.9 or later.
What is the CVSS score of CVE-2021-25641?
CVE-2021-25641 has a CVSS v3.1 base score of 9.8 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2021-25641?
CVE-2021-25641 is classified under CWE-502: Deserialization of Untrusted Data (The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.).
How can I check Maven dependencies for CVE-2021-25641?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=org.apache.dubbo'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-v2rg-8cwr-75g8",
  "modified" : "2022-03-18T17:56:08Z",
  "published" : "2022-03-18T17:56:08Z",
  "aliases" : [ "CVE-2021-25641" ],
  "summary" : "Deserializer tampering in Apache Dubbo",
  "details" : "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.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.apache.dubbo:dubbo"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.5.0"
      }, {
        "fixed" : "2.7.8"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "com.alibaba:dubbo"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.5.0"
      }, {
        "fixed" : "2.6.9"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-25641"
  }, {
    "type" : "WEB",
    "url" : "https://lists.apache.org/thread.html/r99ef7fa35585d3a68762de07e8d2b2bc48b8fa669a03e8d84b9673f3%40%3Cdev.dubbo.apache.org%3E"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-502" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-06-02T19:44:59Z",
    "nvd_published_at" : "2021-06-01T14:15:00Z"
  }
}