Bug 2541916 (CVE-2026-100654)

Summary: CVE-2026-100654 vllm: vLLM: Denial of Service via out-of-range stop token identifiers
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: alinfoot, bbrownin, dtrifiro, weaton
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in vLLM. An authenticated remote attacker can cause a Denial of Service (DoS) by submitting a completion request containing out-of-range stop token identifiers. Because the service does not verify that user-supplied token identifiers fall within the supported vocabulary range of the model, processing these invalid values triggers a fatal error in the underlying processing engine. This causes subsequent requests to fail, rendering the service unavailable until it is restarted.
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Description OSIDB Bzimport 2026-09-26 13:42:49 UTC 
vLLM before 0.29.0 accepts user-controlled stop_token_ids on the OpenAI-compatible POST /v1/completions and POST /v1/chat/completions endpoints but validates only that the values are integers, not that each token id is within the model vocabulary/logits range. When min_tokens > 0, the stop token ids are used as logits indices to suppress stop tokens, so an out-of-range id reaches a CUDA indexing operation (index_put_) and triggers a device-side assertion. An authenticated API user can send a single malformed completion request that returns 500 Internal Server Error and puts EngineCore into a fatal state, causing subsequent requests to fail until the service is restarted (denial of service).