CVE-2025-62515

EUVD-2025-34900 · Published Oct 17, 2025

pyquokka is Vulnerable to Remote Code Execution by Pickle Deserialization via FlightServer

Description

In the FlightServer class of the pyquokka framework, the do_action() method directly uses pickle.loads() to deserialize action bodies received from Flight clients without any sanitization or validation, which results in a remote code execution vulnerability. The vulnerable code is located in pyquokka/flight.py at line 283, where arbitrary data from Flight clients is directly passed to pickle.loads().

Even more concerning, when FlightServer is configured to listen on 0.0.0.0 (as shown in the provided server example at line 339), this allows attackers across the entire network to perform arbitrary remote code execution by sending malicious pickled payloads through the set_configs action.

In addition, the functions cache_garbage_collect, do_put, and do_get also contain vulnerability points where pickle.loads is used to deserialize untrusted remote data. Please review and fix these issues accordingly. This report uses the set_configs action as an example.

Proof of Concept

Step 1:
The victim user starts a FlightServer that binds to the network interface, e.g.:

server = FlightServer("0.0.0.0", location = "grpc+tcp://0.0.0.0:5005")
server.serve()

Step 2:
The attacker can then send malicious pickle dump data through the Flight client connection. The provided PoC demonstrates how an attacker can execute "ls -l" command:

class RCE:
def __reduce__(self):
import os
return (os.system, ('ls -l',))

import pickle
action_body = pickle.dumps(RCE())
action = pyarrow.flight.Action("set_configs", action_body)

When the server receives this payload, the FlightServer.do_action() method calls pickle.loads(action.body.to_pybytes()) on line 283, which triggers the execution of the malicious code through Python's pickle deserialization mechanism. The provided flight_client.py demonstrates a complete PoC that connects to the vulnerable server and executes arbitrary commands through the pickle deserialization vulnerability.

When the vulnerability is reproduced, python flight.py can be run to init the server and then run flight_client.py. There is an attack demo in the attachment.

Impact

Remote code execution on the victim's machine over the network. Once the victim starts the FlightServer with network binding (especially 0.0.0.0), an attacker on the network can gain arbitrary code execution by connecting to the Flight endpoint and sending crafted pickle payloads through the set_configs action. This vulnerability allows for:

Complete system compromise
Data exfiltration
Lateral movement within the network
Denial of service attacks
Installation of persistent backdoors

Mitigation

Replace unsafe deserialization: Replace pickle.loads() with safer alternatives such as:
- JSON serialization for simple data structures
- Protocol Buffers or MessagePack for complex data
- If pickle must be used, implement a custom Unpickler with a restricted find_class() method that only allows whitelisted classes
Network security:
- If the service is intended for internal use only, bind to localhost (127.0.0.1) instead of 0.0.0.0
- Implement authentication and authorization mechanisms
Security warnings: When starting the service on public interfaces, display clear security warnings to inform users about the risks.

Technologies

Pyquokka Pyquokka

Weaknesses

CWE-502

CVSS scores

v3.19.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

MITRE ATT&CK

Inferred

Where this vulnerability fits in an attack

ReconImpact

Initial Access

T1190Exploit Public-Facing Application

References

Potentially impacted assets

See if this affects your attack surface

Latest trending attack

Critical2d ago

Google Brotli decoder - Remote Code Execution via compressed requests (Exploitation Check)

This control is the second step of the Patrowl response to CVE-2026-111497 (Node2Shell). It complements the first control of 22 October 2026, which focused on the Node.js runtime, and does not replace it. Why a second control CVE-2026-111497 is an out-of-bounds write in the Google Brotli decoder, the library that decompresses Brotli ("br") data. It was first published as a Node.js vulnerability, because Node.js bundles this decoder. Later publications showed that the flaw is in the library itself. Every product that embeds an affected version of the decoder is concerned, whatever its language or vendor. A public proof of concept demonstrates code execution. Any server that decompresses request bodies sent with "Content-Encoding: br" exposes the decoder to unauthenticated attackers. Known cases include Express 5 and NestJS 11 on Node.js, Koa and Fastify setups, Bun, Envoy and Istio with request decompression enabled, and any application or reverse proxy that decodes Brotli request bodies with an affected library. The flaw also works in the other direction. A malicious server can compromise an unpatched client that decodes a Brotli response, for example Node.js fetch(), Python clients (requests, httpx, aiohttp, Scrapy) with the Brotli or brotlicffi package, or libcurl builds with Brotli support. What this control checks Patrowl sends small, valid Brotli-compressed requests to each asset and observes whether the server decodes them. The check does not depend on the technology: it detects the behaviour, whatever the stack behind it. These requests are what any legitimate client could send. They never reach the vulnerable code path and cannot affect the availability of the service. How to read the result Potentially impacted means the asset decodes Brotli request bodies: the attack surface is exposed. It does not confirm that the asset is vulnerable. The version of the Brotli decoder in use is not visible from the outside. This check covers applications that parse request bodies on their root path. A Not impacted result does not rule out exposure on other routes, nor on the client side. Checking the versions on the servers remains the only exhaustive verification. Affected and fixed versions Google Brotli 1.0.3 to 1.2.0 are affected, fixed in 1.0.10, 1.1.1 and 1.2.1. Fixed releases of the main products embedding it: Node.js 22.23.4, 24.22.1 and 26.12.1 (end-of-life lines 20.x and older and 25.x receive no fix), Bun 1.4.4, Envoy 1.37.8, 1.38.6, 1.39.3 and 1.40.0, Istio 1.29.9, 1.30.6 and 1.31.2, Python Brotli 1.2.1 and brotlicffi 1.2.1.0. Products that link against the system library depend on the Brotli package of the Linux distribution. Recommendations Update every component that embeds the Brotli decoder (only real fix). Start with the assets flagged by this control. Restart the processes after the update. Rebuild containers, single-executable applications and appliances that bundle an affected runtime or library. Reduce the exposure until the update is deployed. Reject requests with "Content-Encoding: br" at the reverse proxy, load balancer or WAF, case-insensitively and including lists such as "gzip, br". On Envoy and Istio, disable request decompression for Brotli. Review outbound calls. List the features that fetch content from servers you do not control, and patch the services that host them first.