CVE-2025-66455

Unauthenticated RCE via pickle deserialization in LMDeploy DistServe.

• CVSS 9.8
• 502
• Input Validation and Sanitization
• Remote

LMDeploy is a toolkit for compressing, deploying, and serving large language models. Starting in version 0.9.2 and prior to version 0.16.0, LMDeploy's PyTorch DistServe/PD-disaggregation control plane used `recv_pyobj()` to deserialize messages received through a ZeroMQ PULL socket. PyZMQ implements `recv_pyobj()` using Python pickle deserialization, which can execute arbitrary code while reconstructing an object. The peer address used by the receiver was supplied through the `POST /distserve/p2p_connect` HTTP endpoint. An attacker who could reach an affected DistServe API server could cause the server to connect to an attacker-controlled ZeroMQ endpoint and deserialize a crafted pickle payload. API-key authentication is not enabled unless the operator explicitly configures it. As a result, affected DistServe deployments without API keys allowed unauthenticated remote code execution with the privileges of the LMDeploy serving process. This issue affects the PyTorch backend when PD-disaggregation/DistServe is enabled. Ordinary deployments that do not use the affected disaggregated-serving path do not expose this data flow. The fix was released in LMDeploy 0.16.0. Users who cannot upgrade immediately should prevent untrusted clients from reaching `/distserve/*` endpoints, restrict the DistServe HTTP and ZeroMQ control planes to trusted cluster networks, configure API-key authentication, and block arbitrary outbound ZeroMQ connections from serving nodes. These measures reduce exposure but do not make pickle deserialization safe.

CVE

CVE-2025-66455

CWE

502

CVSS base score

9.8

Published

2026-09-18

OWASP

A08 Software and Data Integrity Failures

Orthogonal defect classification

Timing/Serialization

Code defect classification

Serialization Issues

Category

Input Validation and Sanitization

Subcategory

Insecure Parsing or Deserialization

Accessibility scope

Remote

Impact

Arbitrary Code Execution

Affected component

LMDeploy

Fixed by upgrading

Yes

Solution

Upgrade LMDeploy to version 0.16.0 or newer.

import zmq
from flask import Flask, request, jsonify

app = Flask(__name__)

@app.route('/distserve/p2p_connect', methods=['POST'])
def p2p_connect():
    peer_addr = request.json.get('peer_addr')
    if not peer_addr:
        return jsonify({'error': 'missing peer_addr'}), 400

    ctx = zmq.Context()
    socket = ctx.socket(zmq.PULL)
    socket.connect(peer_addr)

    # VULNERABLE: using pickle deserialization on untrusted data
    obj = socket.recv_pyobj()
    # process obj...
    return jsonify({'status': 'ok'}), 200

import zmq
import json
from flask import Flask, request, jsonify

app = Flask(__name__)

@app.route('/distserve/p2p_connect', methods=['POST'])
def p2p_connect():
    peer_addr = request.json.get('peer_addr')
    if not peer_addr:
        return jsonify({'error': 'missing peer_addr'}), 400

    ctx = zmq.Context()
    socket = ctx.socket(zmq.PULL)
    socket.connect(peer_addr)

    # FIX: receive raw bytes and safely deserialize JSON
    raw = socket.recv()
    try:
        obj = json.loads(raw.decode('utf-8'))
    except (json.JSONDecodeError, UnicodeDecodeError):
        return jsonify({'error': 'invalid payload'}), 400
    # process obj...
    return jsonify({'status': 'ok'}), 200

__VAITP_MODEL_REFUSED__

@misc{vaitp:cve202566455,
  title        = {{Unauthenticated RCE via pickle deserialization in LMDeploy DistServe.}},
  author       = {Bogaerts, Fr\'ed\'eric and Ivaki, Naghmeh and Fonseca, Jos\'e},
  year         = {2026},
  note         = {VAITP Python Vulnerability Dataset, entry CVE-2025-66455},
  howpublished = {\url{https://netpack.pt/vaitp/vulnerability/CVE-2025-66455/}}
}