Summary
fabric-sdk-java has ObjectInputStream.readObject() without ObjectInputFilter, which allows Java deserialization RCE
This advisory covers the deprecated fabric-sdk-java client SDK. Channel.java implements readObject() and exposes deSerializeChannel() which call ObjectInputStream.readObject() on untrusted byte arrays without configuring an ObjectInputFilter. This is the classic Java deserialization RCE pattern.
Note: fabric-sdk-java is deprecated and maintained in https://github.com/hyperledger/fabric-sdk-java. Filing here as that repo does not have private vulnerability reporting enabled.
Affected Code
// src/main/java/org/hyperledger/fabric/sdk/Channel.java
private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
in.defaultReadObject(); // No ObjectInputFilter configured
}
public Channel deSerializeChannel(byte[] channelBytes)
throws IOException, ClassNotFoundException, InvalidArgumentException {
ObjectInputStream ois = new ObjectInputStream(new ByteArrayInputStream(channelBytes));
Channel channel = (Channel) ois.readObject(); // Untrusted bytes deserialized
return channel;
}
Attack Vector
An attacker who can supply crafted serialized Channel bytes to the client application, for example, by compromising a local channel file, injecting data through an application that accepts Channel bytes from external sources, or exploiting a separate write primitive, can achieve RCE via gadget chain exploitation when deSerializeChannel() processes those bytes. The risk is highest in deployments that accept Channel data from sources outside the client's direct control. Note: channel data is not transmitted from Fabric peers; this is a client-side deserialization surface.
Proof of Concept
// Generate malicious payload with ysoserial:
// java -jar ysoserial.jar CommonsCollections6 "touch /tmp/pwned" > malicious_channel.ser
// Victim code:
byte[] maliciousBytes = Files.readAllBytes(Paths.get("malicious_channel.ser"));
Channel channel = client.deSerializeChannel(maliciousBytes); // RCE fires here
Notes on Deprecation
fabric-sdk-java is deprecated as of Hyperledger Fabric v2.5 (replaced by org.hyperledger.fabric:fabric-gateway). However, organizations that have not yet migrated remain fully exposed. Automated dependency scanners (Snyk, Dependabot) cannot alert users without a published GHSA. This advisory is filed to ensure those users are notified and directed to migrate.
Resources
- CWE-502: Deserialization of Untrusted Data
- Migration guide: https://hyperledger.github.io/fabric-gateway/
Credits
Found by Martin Brodeur (brodmart) via independent security research.
Impact
Untrusted serialized data is processed by a deserializer that can instantiate arbitrary objects or execute code as a side effect. Typical impact: arbitrary code execution or logic abuse.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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See it in your environmentNew to Kodem? Get a demo →Remediation advice
For the deprecated SDK: add ObjectInputFilter to whitelist only expected classes:
ObjectInputFilter filter = ObjectInputFilter.Config.createFilter(
"org.hyperledger.fabric.sdk.*;java.util.*;java.lang.*;!*"
);
ois.setObjectInputFilter(filter);
The recommended remediation is migration to org.hyperledger.fabric:fabric-gateway, which does not use Java serialization.
Frequently Asked Questions
- What is CVE-2026-41586? CVE-2026-41586 is a critical-severity insecure deserialization vulnerability in org.hyperledger.fabric-sdk-java:fabric-sdk-java (maven), affecting versions >= 1.0.0, <= 2.2.26. No fixed version is listed yet. Untrusted serialized data is processed by a deserializer that can instantiate arbitrary objects or execute code as a side effect.
- Which versions of org.hyperledger.fabric-sdk-java:fabric-sdk-java are affected by CVE-2026-41586? org.hyperledger.fabric-sdk-java:fabric-sdk-java (maven) versions >= 1.0.0, <= 2.2.26 is affected.
- Is there a fix for CVE-2026-41586? No fixed version is listed for CVE-2026-41586 yet. Monitor the advisory for updates and apply mitigations in the interim.
- Is CVE-2026-41586 exploitable, and should I be worried? Whether CVE-2026-41586 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-41586 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-41586? No fixed version is listed yet. In the interim: Avoid deserializing data from untrusted sources. If deserialization is required, use a format that does not support code execution and validate the input strictly.