New Deserialization Vulnerability in Ruby Workers Could Enable Full System Compromise

Ruby Deserialization Vulnerability A Ruby background job processing system has been found to have a critical Remote Code Execution (RCE) vulnerability This article explores deserialization vulnerability ruby. . Unsafe JSON deserialization is the source of the vulnerability, enabling the conversion of untrusted input into executable objects.

This problem draws attention to the hidden risks associated with deserialization in Ruby environments, where deterministic command execution in a background worker context can result from a single line of code. Rather than being caused by memory corruption or obscure gadget chains, the vulnerability stems from design-level trust assumptions. When the application uses the Oj gem to process JSON, an issue occurs. Oj.load deserializes untrusted input to create fully functional Ruby objects with methods and system access.

This opens the door for complete system compromise by bridging the gap between data and code. Vulnerability mechanics and exploitation of a Ruby background job processing system (source: NullSecurityX) The main source of the problem is the application's background job pattern, which stores user-controlled input as a JSON payload that a background worker subsequently deserializes. Data = Oj.load(job.payload), the crucial line of code, deserializes objects rather than just parsing JSON.

Researchers at NullSecurityX claim that Oj.load can reconstruct objects using specific JSON directives, like {\",^o": “ClassName." This enables an attacker to return a functional object, inject variables, and allocate a class instance.

Critical Unsafe JSON Deserialization Object Injection Vulnerability Type Risk Level Attack Vector Remote Code Execution (RCE) Critical Malicious Payload in Background Jobs via High Capability-Based Dynamic Dispatch Command Injection The application evaluates the object using capability-based dynamic dispatch after it has been rebuilt. The object is permitted to run a particular method, like run_find, if it exposes it. This design flaw becomes dangerous when a utility class, like Node, contains an insecure method that invokes Open3.capture3.

An attacker can create a JSON payload that instructs Oj.load to deserialize a Node object using malicious arguments, like shell commands masquerading as find command arguments. There is no need for injection tricks because the exploitation chain is completely deterministic.

The payload is saved, rebuilt, and then run, enabling the execution of any shell command. This makes it possible for unauthorized attackers to take over background processes, which frequently leads to a total system compromise. Area Status/Indicator Important Information Note/Mitigation Ruby Oj in object mode Vulnerable and unsafe Deserialization of Oj.load Utilize Oj.safe_load or enforce stringent parsing Context Work Queue Risk Dynamic reaction to?

abuse of dispatch Use clear, hardcoded job handling instead. JSON Pattern Malicious IOC ("^o\Node") instantiation of objects shows an attempt at exploitation Untrustworthy Process Implementation IOC find / -maxdepth 0 -exec sh -c Unexpected worker shell execution Developers must treat serialized input as hostile by default in order to mitigate this vulnerability. To guarantee that data is handled safely, NullSecurityX suggests using strict parsing modes or Oj.safe_load.

Explicit job handling should also take the place of dynamic dispatch, and operating system commands with user-controlled arguments should never be executed. X, LinkedIn, and LinkedIn for daily ZeroOwl. To have your stories featured, get in touch with us.