CVE-2025-61765 in python-socketio
Summary
by MITRE • 10/06/2025
python-socketio is a Python implementation of the Socket.IO realtime client and server. A remote code execution vulnerability in python-socketio versions prior to 5.14.0 allows attackers to execute arbitrary Python code through malicious pickle deserialization in multi-server deployments on which the attacker previously gained access to the message queue that the servers use for internal communications. When Socket.IO servers are configured to use a message queue backend such as Redis for inter-server communication, messages sent between the servers are encoded using the `pickle` Python module. When a server receives one of these messages through the message queue, it assumes it is trusted and immediately deserializes it. The vulnerability stems from deserialization of messages using Python's `pickle.loads()` function. Having previously obtained access to the message queue, the attacker can send a python-socketio server a crafted pickle payload that executes arbitrary code during deserialization via Python's `__reduce__` method. This vulnerability only affects deployments with a compromised message queue. The attack can lead to the attacker executing random code in the context of, and with the privileges of a Socket.IO server process. Single-server systems that do not use a message queue, and multi-server systems with a secure message queue are not vulnerable. In addition to making sure standard security practices are followed in the deployment of the message queue, users of the python-socketio package can upgrade to version 5.14.0 or newer, which remove the `pickle` module and use the much safer JSON encoding for inter-server messaging.
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Analysis
by VulDB Data Team • 10/25/2025
The vulnerability CVE-2025-61765 represents a critical remote code execution flaw in the python-socketio library affecting versions prior to 5.14.0. This security issue specifically targets multi-server deployments that utilize message queue backends such as Redis for inter-server communication. The vulnerability operates through a sophisticated exploitation chain that requires initial compromise of the message queue system, followed by crafting malicious pickle payloads that leverage Python's deserialization mechanisms. The attack vector demonstrates a classic example of insecure deserialization where trusted internal communications become attack surfaces when improper security controls are in place.
The technical implementation of this vulnerability stems from the library's reliance on Python's pickle module for serializing and deserializing inter-server messages. When Socket.IO servers are configured with message queue backends, all internal communications pass through these queues and are encoded using pickle serialization. The flaw occurs because servers automatically deserialize messages received through these queues without proper validation or sanitization, directly invoking pickle.loads() on potentially malicious data. This deserialization process is particularly dangerous because Python's pickle protocol supports the _reduce_ method which can execute arbitrary code during the deserialization process, making it a prime target for attackers who can inject crafted payloads.
The operational impact of this vulnerability is severe and directly correlates with the compromise of the message queue infrastructure. Attackers who gain access to the message queue can construct malicious pickle payloads that execute arbitrary code within the context of the Socket.IO server processes. This privilege escalation allows attackers to potentially compromise the entire server infrastructure, extract sensitive data, or establish persistent access points. The vulnerability's scope is limited to deployments where the message queue has been previously compromised, meaning single-server installations or multi-server systems with properly secured message queues remain unaffected. This characteristic makes the vulnerability particularly insidious as it requires attackers to first establish access to internal systems before exploiting the serialization flaw.
Security practitioners should recognize this vulnerability as a direct violation of several security principles including the principle of least privilege and secure coding practices for data deserialization. From a CWE perspective, this vulnerability aligns with CWE-502 which addresses deserialization of untrusted data, and CWE-749 which covers exposed dangerous method or function calls. The attack pattern also maps to ATT&CK techniques such as T1059.001 for command and script interpreter and T1133 for external remote services. Organizations should implement comprehensive security measures including network segmentation, message queue access controls, and regular security assessments to prevent initial compromise of these internal communication channels. The recommended mitigation strategy involves upgrading to python-socketio version 5.14.0 or later, which eliminates the pickle module dependency and implements safer JSON-based serialization for inter-server communications. Additionally, organizations should enforce strict access controls on message queue systems and implement monitoring for unusual message patterns that might indicate exploitation attempts.