vLLM Affected by Unauthenticated OOM Denial of Service via Unbounded `n` Parameter in OpenAI API Server
Priority LOW 29CWE-770Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Partial Red Hat: 3 fixed, 2 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-770.
Summary
vLLM is an inference and serving engine for large language models (LLMs). From 0.1.0 to before 0.19.0, a Denial of Service vulnerability exists in the vLLM OpenAI-compatible API server. Due to the lack of an upper bound validation on the n parameter in the ChatCompletionRequest and CompletionRequest Pydantic models, an unauthenticated attacker can send a single HTTP request with an astronomically large n value. This completely blocks the Python asyncio event loop and causes immediate Out-Of-Memory crashes by allocating millions of request object copies in the heap before the request even reaches the scheduling queue. This vulnerability is fixed in 0.19.0.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00438 38th percentileScored 2026-11-07
Fix Partial vllm (vllm-project): 0.19.0vllm (PyPI): 0.19.0Red Hat: 8 advisoriesRed Hat: 3 fixed, 2 without a fix
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| vllm-project | vllm | 0.1.0 to before 0.19.0 | 0.19.0 | Patch available | CNA |
| — | vllm (PyPI) | 0.1.0 to before 0.19.0 | 0.19.0 | Patch available | GHSA-3mwp-wvh9-7528 |
- vllm Vendorvllm-project Affected 0.1.0 to before 0.19.0 Fixed in 0.19.0 Patch available CNA
- vllm (PyPI) Vendor— Affected 0.1.0 to before 0.19.0 Fixed in 0.19.0 Patch available GHSA-3mwp-wvh9-7528
Remediation
- Fix · CNA vllm (vllm-project) Fixed in 0.19.0
- Fix · GHSA-3mwp-wvh9-7528 vllm (PyPI) Fixed in 0.19.0 Advisory →
Red Hat 8 advisories
- RHSA-2026:59151 Released 2026-08-24 · Red Hat rating ImportantRed Hat Enterprise Linux AI 3.4.4 enhancement update
- Red Hat Enterprise Linux AI 3.4 registry.redhat.io/rhelai3/bootc-aws-cuda-rhel9, registry.redhat.io/rhelai3/bootc-azure-cuda-rhel9, registry.redhat.io/rhelai3/bootc-azure-rocm-rhel9 +3
- RHSA-2026:59144 Released 2026-08-24 · Red Hat rating ImportantRed Hat Enterprise Linux AI 3.4.4 enhancement update
- Red Hat Enterprise Linux AI 3.4 registry.redhat.io/rhelai3/disk-image-cuda-rhel9
- RHSA-2026:57390 Released 2026-08-20 · Red Hat rating ImportantRed Hat AI Inference 3.4.4 (rocm)
- Red Hat AI Inference Server 3.4 registry.redhat.io/rhaii/vllm-rocm-rhel9
Show 5 more Red Hat advisories
- RHSA-2026:57389 Released 2026-08-20 · Red Hat rating ImportantRed Hat AI Inference 3.4.4 (cuda)
- Red Hat AI Inference Server 3.4 registry.redhat.io/rhaii/vllm-cuda-rhel9
- RHSA-2026:57387 Released 2026-08-20 · Red Hat rating ImportantRed Hat AI Inference 3.4.4 (spyre)
- Red Hat AI Inference Server 3.4 registry.redhat.io/rhaii/vllm-spyre-rhel9
- RHSA-2026:57380 Released 2026-08-20 · Red Hat rating ImportantRed Hat AI Inference 3.4.4 (cpu)
- Red Hat AI Inference Server 3.4 registry.redhat.io/rhaii/vllm-cpu-rhel9
- RHSA-2026:36006 Released 2026-07-06 · Red Hat rating ImportantRed Hat AI Inference Server 3.2.2 (ROCm)
- Red Hat AI Inference Server 3.2 registry.redhat.io/rhaiis/vllm-rocm-rhel9
- RHSA-2026:36005 Released 2026-07-06 · Red Hat rating ImportantRed Hat AI Inference Server 3.2.2 (CUDA)
- Red Hat AI Inference Server 3.2 registry.redhat.io/rhaiis/vllm-cuda-rhel9
Vendor assessments
Red Hat
Red Hat rating: Important. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat AI Inference Server | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift AI (RHOAI) | Affected | No fix yet: Fix deferred |
| Red Hat AI Inference Server 3.2 | Fixed | RHSA-2026:36005, RHSA-2026:36006 |
| Red Hat AI Inference Server 3.4 | Fixed | RHSA-2026:57380, RHSA-2026:57387, RHSA-2026:57389, RHSA-2026:57390 |
| Red Hat Enterprise Linux AI 3.4 | Fixed | RHSA-2026:59144, RHSA-2026:59151 |
Timeline
- 2026-10-02 Threatist record created from CVE-2026-34756
- 2026-10-03 Alias added: GHSA-3mwp-wvh9-7528
- 2026-10-25 EPSS moved to the below the 50th percentile
References
Patch 3
Other 7
- https://access.redhat.com/errata/RHSA-2026:36005
- https://access.redhat.com/errata/RHSA-2026:36006
- https://access.redhat.com/security/cve/CVE-2026-34756
- https://bugzilla.redhat.com/show_bug.cgi?id=2455425
- https://github.com/pypa/advisory-database/tree/main/vulns/vllm/PYSEC-2026-2298.yaml
- https://github.com/vllm-project/vllm
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34756.json
More vllm-project vulnerabilities
- TI-2024-10229 Remote Code Execution in vllm-project/vllm CVSS 3.0CRITICAL 9.8
- TI-2024-08404 Remote Code Execution in vllm-project/vllm CVSS 3.1CRITICAL 9.8
- TI-2026-36017 vLLM: OpenAI auth bypass CVSS 3.1CRITICAL 9.1
- TI-2026-63056 vLLM before 0.28.0 Denial of Service via negative token ID CVSS 4.0HIGH 8.7
- TI-2026-04308 Hardcoded trust_remote_code=True in vllm-project/vllm Bypasses User Security Control CVSS 3.0HIGH 8.8
- TI-2026-39137 vLLM: Remote DoS in vLLM via Invalid Recovered Token Reinjection CVSS 3.1HIGH 7.5
Sources
- CVE-2026-34756 · CVE Program
- CVE-2026-34756 · NVD
- FIRST EPSS
- GHSA-3mwp-wvh9-7528 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-34756 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences