AIKIDO-2026-543696
sglang is vulnerable to Deserialization of Untrusted Data
98
CVE Score
Critical
Deserialization of Untrusted Data
TL;DR
The /update_weights_from_tensor HTTP endpoint deserializes a base64-encoded pickle payload through the SafeUnpickler class in python/sglang/srt/utils/common.py. SafeUnpickler allowlists the entire builtins module prefix and its denylist omits __import__ and getattr, so a crafted payload chains builtins.__import__ and builtins.getattr inside a pickle REDUCE operation to resolve os.system and run arbitrary commands. The endpoint is marked AuthLevel.ADMIN_OPTIONAL, so it accepts unauthenticated requests whenever the server runs without a configured API key.
How do I fix this?
Upgrade the sglang library to the patch version.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and the server is deployed without an API key so the /update_weights_from_tensor endpoint accepts unauthenticated requests.
Package
Versions
0.1.3 - 0.5.19
Fixed in 0.5.20Background info
sglang is vulnerable to Deserialization of Untrusted Data in versions 0.1.3 - 0.5.19.
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