fix(security): replace unsafe pickle.loads with SafeUnpickler for CVE-2026-3989 (sgl-project#20904)

Author: zwang86

docs/developer_guide/contribution_guide.md

@@ -166,6 +166,7 @@ Users listed in [CI_PERMISSIONS.json](https://github.com/sgl-project/sglang/blob
   - If a single test file run longer than 500 seconds, split it into multiple smaller files (e.g., `test_eagle_infer_a.py`, `test_eagle_infer_b.py`).
   - If a single job in a github workflow runs longer than 30 mins, split it into smaller jobs/steps.
   - Reuse server launches in your unit tests to make tests run faster.
+- Never use `pickle.loads()`, `pickle.load()`, or `recv_pyobj()` to deserialize untrusted or network-received data. Python's [pickle module is not secure](https://docs.python.org/3/library/pickle.html) — it can execute arbitrary code during deserialization. Use safe serialization formats such as [msgpack](https://github.com/jcrist/msgspec) or JSON instead.
 - When supporting new hardware or features, follow these guidelines:
   - Do not drastically change existing code.
   - Always prefer new files to introduce specific components for your new hardware (e.g., `allocator_ascend.py`).

python/sglang/srt/utils/common.py

@@ -2144,6 +2144,11 @@ def find_class(self, module, name):
         )
 
 
+def safe_pickle_load(fp):
+    """Drop-in replacement for pickle.load() that blocks unsafe class loading."""
+    return SafeUnpickler(fp).load()
+
+
 def debug_timing(func):
     # todo: replace with a more organized instrumentation
     def wrapper(*args, **kwargs):

scripts/playground/replay_request_dump.py

@@ -10,7 +10,6 @@
 import argparse
 import glob
 import json
-import pickle
 import time
 from concurrent.futures import ThreadPoolExecutor
 from dataclasses import asdict
@@ -19,6 +18,7 @@
 import requests
 
 from sglang.benchmark.utils import set_ulimit
+from sglang.srt.utils.common import safe_pickle_load
 from sglang.utils import get_exception_traceback
 
 
@@ -54,7 +54,8 @@ def normalize_request_data(json_data):
 def read_records(files):
     records = []
     for f in files:
-        tmp = pickle.load(open(f, "rb"))
+        with open(f, "rb") as fh:
+            tmp = safe_pickle_load(fh)
         if isinstance(tmp, dict) and "requests" in tmp:
             records.extend(tmp["requests"])
         else: