Python-socket.io module flaw lets attackers access business servers

A design flaw in python-socket.io has turned a feature built for scaling web applications into a wide-open opportunity for attackers to run a remote code execution (RCE) and gain full administrative control of critical business servers.

The flaw — CVE-2025-61765 — was patched three weeks ago by the maintainers after researchers at BlueRock reported the flaw.

According to an Oct. 23 blog post by BlueRock, the bug affects multi-server deployments that use common message brokers such as Redis, Kafta, and RabbitMQ.

“This isn’t about one CVE,” said Bob Tinker, chief executive officer at BlueRock. “Wherever Python apps run, including agentic AI and MCP, web micro-services and real-time messaging stacks, data deserialization is a direct path to remote code execution."

Tinker added that it’s especially concerning in the case of agentic AI and MCP, which the industry has been rolling out at breakneck speed, with little regard to security.

“Every customer we talk to is worried about this,” said Tinker. “The idea that CVE-by-CVE patching can keep pace is, quite frankly, laughable. And it doesn’t address the underlying structural risks. What customers need are CVE-agnostic runtime guardrails to sandbox apps and prevent unsanctioned behavior from happening in the first place."

Python’s in a bit of a pickle

The BlueRock researchers explained that the bug stems from a fundamental misunderstanding of Python's “pickle” module. The pickle module was designed for serializing and deserializing trusted Python objects: it was never intended to be a secure format for communicating between systems that don't implicitly trust one another. 

John Carberry, solution sleuth at Xcape, Inc., explained that the core risk here is that a malicious pickle payload could let an attacker run code with server privileges, potentially leading to complete application compromise if the queue is misconfigured.

“GitHub Teams should promptly update, secure message queues (authentication, access control, and no public access), favor safer formats (JSON/MessagePack) over pickle, and implement signing/verification for inter-process messages,” said Carberry. “Also, regularly audit for suspicious queue writes and rotate credentials often. If your servers are “pickling” across a shared queue, you’re one poisoned message away from running the attacker’s code.”

Darren Meyer, security research advocate at Checkmarx, added that if an affected application uses the vulnerable library, an attacker with access to a connected datastore, such as Redis, could exploit it to execute arbitrary code embedded within data objects, effectively gaining the same privileges as the application itself.

“While not all apps are affected, those depending on python-socket.io should upgrade to a patched version immediately,” said Meyer. “It's also important to strengthen defenses around associated datastores and review stored data for potential compromise. This issue highlights yet another example of a library misusing Python's 'pickle' system for data communication, which should never be used to load untrusted data."