CVE-2026-65423 – o6 Automation open62541 Integer Overflow or Wraparound

Immediately identify and inventory all applications and services that utilize the Acme Serialization Framework (ASF) library. Prioritize systems that are publicly accessible or handle untrusted input.
For identified systems, restrict network access to the greatest extent possible. If feasible, disconnect affected systems from external networks or place them behind stringent firewall rules that block all non-essential inbound and outbound connections.
Implement emergency Web Application Firewall (WAF) or Intrusion Prevention System (IPS) rules to block requests containing common deserialization gadget chains or unusually large serialized object payloads directed at endpoints known to process serialized data. This is a temporary measure and may not be exhaustive.
Monitor system logs, application logs, and network traffic for any signs of exploitation attempts, unusual process execution, or unexpected network connections originating from systems using ASF. Look for anomalies such as shell command execution, file modifications, or unusual outbound connections.
Isolate any systems suspected of compromise immediately to prevent lateral movement and further damage. Take forensic images if necessary before making changes.

2. PATCH AND UPDATE INFORMATION

This vulnerability affects Acme Serialization Framework (ASF) versions 3.0.0 through 3.5.2. The vendor has released a security update that addresses the deserialization vulnerability.
The recommended remediation is to update ASF to version 3.5.3 or later, or to the next major release, ASF 4.0.0 or later, which includes a comprehensive fix for this issue. These versions implement stricter type validation during deserialization and introduce allow-listing capabilities by default.
For Java applications using Maven, update the dependency in your pom.xml:
<dependency>
<groupId>com.acme</groupId>
<artifactId>acme-serialization-framework</artifactId>
<version>3.5.3</version>
</dependency>
For Java applications using Gradle, update the dependency in your build.gradle:
dependencies {
implementation 'com.acme:acme-serialization-framework:3.5.3'
}
After updating the library, thoroughly recompile and redeploy all affected applications. Conduct comprehensive regression testing to ensure functionality is not impacted by the update.
If direct patching is not immediately possible, consider moving to the Mitigation Strategies section for temporary controls.

3. MITIGATION STRATEGIES

If immediate patching is not feasible, implement the following mitigation strategies:
Disable deserialization of untrusted data: Where possible, refactor applications to avoid deserializing data from untrusted sources. If data must be deserialized, ensure it originates from authenticated and trusted internal services.
Implement allow-listing for deserialized classes: Configure the ASF deserializer to only allow a predefined set of safe classes to be deserialized. This can typically be done by providing a custom ObjectInputStream or equivalent mechanism that strictly validates class types before loading. For example, in ASF 3.5.2 and earlier, you might need to implement a custom deserialization filter.
Restrict network access to deserialization endpoints: Ensure that any application endpoints that expose ASF deserialization functionality are not directly accessible from the internet or untrusted networks. Implement strict network segmentation and firewall rules.
Run applications with least privilege: Ensure the user account or service account running the application has only the minimum necessary permissions to perform its functions. This can limit the impact of a successful RCE exploit.
Implement application-level input validation: While deserialization vulnerabilities bypass typical input validation, robust validation of incoming data before it reaches any deserialization logic can help filter out malicious payloads if the data format is known.

4. DETECTION METHODS

Monitor for unexpected process creation: Look for unusual child processes spawned by the application server or the application itself. This includes shell processes (e.g., cmd.exe, bash), scripting interpreters (e.g., powershell.exe, python), or other unexpected executables.
Analyze network traffic for suspicious serialized payloads: Use network intrusion detection systems (NIDS) or packet sniffers to identify network traffic containing large, malformed, or unusual serialized object streams directed at application endpoints. Look for patterns indicative of known deserialization gadget chains.
Review application and system logs for errors: Monitor for deserialization errors,