CVE-2025-62515: pyquokka RCE Vulnerability

CVE-2025-62515 Overview

CVE-2025-62515 is a critical insecure deserialization vulnerability in pyquokka, a framework for making data lakes work for time series data. The vulnerability exists in the FlightServer class which directly uses pickle.loads() to deserialize action bodies received from Flight clients without any sanitization or validation in the do_action() method. This allows attackers to execute arbitrary code remotely by sending malicious pickled payloads.

Critical Impact

Remote attackers can achieve arbitrary code execution on systems running pyquokka FlightServer configured to listen on 0.0.0.0, compromising confidentiality, integrity, and availability of affected systems.

Affected Products

• pyquokka versions 0.3.1 and prior
• Systems running FlightServer configured to listen on network interfaces (e.g., 0.0.0.0)
• Deployments exposed to untrusted network traffic

Discovery Timeline

• 2025-10-17 - CVE-2025-62515 published to NVD
• 2025-10-21 - Last updated in NVD database

Technical Details for CVE-2025-62515

Vulnerability Analysis

The vulnerability stems from the unsafe use of Python's pickle module for deserializing untrusted data. Python's pickle.loads() function is inherently dangerous when processing data from untrusted sources, as it can execute arbitrary Python code during the deserialization process. In pyquokka's FlightServer implementation, user-controlled data received from Flight clients is passed directly to pickle.loads() without any form of validation, sanitization, or type checking.

The vulnerable code is located in pyquokka/flight.py at line 283, specifically within the do_action() method. When the FlightServer receives a set_configs action, it deserializes the action body using pickle, creating an exploitable attack surface. Additional vulnerable code paths exist in the cache_garbage_collect, do_put, and do_get functions, which also use pickle.loads to deserialize remote data.

When FlightServer is configured to listen on 0.0.0.0 (all network interfaces), any attacker with network access can send specially crafted malicious pickled payloads to trigger arbitrary code execution on the server.

Root Cause

The root cause is the use of Python's pickle.loads() to deserialize untrusted data from remote clients (CWE-502: Deserialization of Untrusted Data). Python's pickle module documentation explicitly warns that pickle is not secure against erroneous or maliciously constructed data and should never be used to deserialize data from untrusted sources. The pyquokka FlightServer implementation ignores this guidance, directly passing client-supplied data to pickle.loads() across multiple code paths.

Attack Vector

The attack vector is network-based, requiring no authentication or user interaction. An attacker can exploit this vulnerability by:

1. Identifying a pyquokka FlightServer instance exposed on the network
2. Crafting a malicious pickle payload that executes arbitrary Python code when deserialized
3. Sending the payload through one of the vulnerable endpoints (set_configs action, cache_garbage_collect, do_put, or do_get)
4. Achieving remote code execution with the privileges of the FlightServer process

The exploitation is straightforward for attackers familiar with Python pickle deserialization attacks, as numerous public resources and tools exist for generating malicious pickle payloads.

Detection Methods for CVE-2025-62515

Indicators of Compromise

• Unexpected outbound network connections from pyquokka FlightServer processes
• Unusual process spawning from Python processes running FlightServer
• Suspicious payloads in Apache Arrow Flight traffic containing pickle magic bytes (\\x80 followed by protocol version)
• Anomalous system resource usage by FlightServer processes
• Unexpected files created or modified in locations accessible by the FlightServer process

Detection Strategies

• Monitor network traffic to FlightServer endpoints for suspicious serialized data patterns
• Implement application-level logging for all do_action, do_put, and do_get operations
• Deploy endpoint detection and response (EDR) solutions to identify post-exploitation activity
• Use network intrusion detection systems (NIDS) with rules targeting pickle deserialization attacks

Monitoring Recommendations

• Enable verbose logging in pyquokka FlightServer to capture all incoming requests
• Monitor process creation events from Python interpreter processes
• Implement network segmentation to isolate FlightServer instances from untrusted networks
• Set up alerts for any outbound connections initiated by FlightServer processes to unexpected destinations

How to Mitigate CVE-2025-62515

Immediate Actions Required

• Restrict FlightServer network binding to trusted interfaces only (avoid 0.0.0.0)
• Implement network-level access controls to limit which hosts can connect to FlightServer
• Deploy firewall rules to block unauthorized access to FlightServer ports
• Consider disabling FlightServer functionality if not actively required
• Monitor for suspicious activity on systems running affected pyquokka versions

Patch Information

No official patch is currently available for this vulnerability. Users should monitor the GitHub Security Advisory for updates on remediation from the maintainers. Until a patch is released, implement the workarounds and mitigations described below.

Workarounds

• Bind FlightServer to 127.0.0.1 or other trusted interfaces instead of 0.0.0.0
• Implement network segmentation to isolate pyquokka deployments from untrusted networks
• Use a VPN or SSH tunnel for remote access to FlightServer instead of direct network exposure
• Deploy a reverse proxy with authentication in front of FlightServer to control access
• Consider replacing pickle serialization with safer alternatives like JSON if modifying the source code locally

# Network access control example using iptables
# Restrict FlightServer port access to trusted IP addresses only
iptables -A INPUT -p tcp --dport 8815 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 8815 -j DROP