CVE-2026-34756

MEDIUMPre-NVD 6.56.5—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4%, top 67% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.5Exploit: None knownExposed: 0

A fix is available — apply it.

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.

CVSS v3
6.5
EG Score
6.5(medium)
EG Risk
29(Track)
EG Risk 29/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity65% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
36%
KEV
Not listed

Published

April 6, 2026

Last Modified

August 25, 2026

Advisory Details (8)

Auto-updated Jul 7, 2026
Patch available. Sources: github, redhat, github_commit, github_pr.
redhat Patch Available
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34756.json
redhat

2455425 – (CVE-2026-34756) CVE-2026-34756 vllm: vLLM: Denial of Service via excessively large 'n' parameter in OpenAI-compatible API

https://bugzilla.redhat.com/show_bug.cgi?id=2455425
redhat Patch Available

cve-details

https://access.redhat.com/security/cve/CVE-2026-34756
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:36006
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:36005
github Patch Available

OOM Denial of Service via Unbounded `n` Parameter in OpenAI API Server · Advisory · vllm-project/vllm · GitHub

https://github.com/vllm-project/vllm/security/advisories/GHSA-3mwp-wvh9-7528
github_pr

fix(security): Add VLLM_MAX_N_SEQUENCES environment variable and enforce limit

Fix merged in vllm-project/vllm PR #37952 on 2026-03-27 — awaiting tagged release

https://github.com/vllm-project/vllm/pull/37952
github_commit

commit b111f8a61f10 (vllm-project/vllm)

Fix landed in vllm-project/vllm commit b111f8a61f10 — awaiting tagged release

https://github.com/vllm-project/vllm/commit/b111f8a61f100fdca08706f41f29ef3548de7380

Vendor Advisories for CVE-2026-34756(9)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(8)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatrhelai3/disk-image-cuda-rhel9:17873107172026-08-24redhat
redhatrhelai3/bootc-rocm-rhel9:17872440062026-08-24redhat
redhatrhaii/vllm-rocm-rhel9:17871517742026-08-20redhat
redhatrhaii/vllm-spyre-rhel9:17871518402026-08-20redhat
redhatrhaii/vllm-cuda-rhel9:17871517712026-08-20redhat
redhatrhaii/vllm-cpu-rhel9:17871517692026-08-20redhat
redhatrhaiis/vllm-rocm-rhel9:17829512442026-07-06redhat
redhatrhaiis/vllm-cuda-rhel9:17829510122026-07-06redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFixed inDependents
vllm0.1.0 ... 0.9.2 (79 versions)0.19.0—

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 9× in last 7d / 40× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 186 total refreshes for this CVE.

  1. 2026-09-18 19:28 UTCEPSS rescore
  2. 2026-09-18 19:28 UTCEPSS rescore
  3. 2026-09-17 19:30 UTCEPSS rescore
  4. 2026-09-16 14:08 UTCEPSS rescore
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  6. 2026-09-15 03:11 UTCEPSS rescore
  7. 2026-09-13 16:47 UTCEPSS rescore
  8. 2026-09-13 11:54 UTCOSV refresh
  9. 2026-09-12 15:01 UTCEPSS rescore
  10. 2026-09-11 14:53 UTCEPSS rescore
  11. 2026-09-11 09:37 UTCEPSS rescore
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  14. 2026-09-07 16:01 UTCEPSS rescore
  15. 2026-09-06 13:47 UTCEPSS rescore
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  17. 2026-09-02 14:12 UTCEPSS rescore
  18. 2026-09-01 13:53 UTCEPSS rescore
  19. 2026-09-01 04:39 UTCEPSS rescore
  20. 2026-08-30 19:17 UTCEPSS rescore
  21. 2026-08-30 01:22 UTCEPSS rescore
  22. 2026-08-28 21:41 UTCEPSS rescore
  23. 2026-08-27 14:25 UTCEPSS rescore
  24. 2026-08-26 14:46 UTCEPSS rescore
  25. 2026-08-25 13:49 UTCEPSS rescore
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  1. 2026-08-25 13:25 UTCEG score recompute
  2. 2026-08-25 13:25 UTCVendor advisory
  3. 2026-08-25 12:22 UTCEG score recompute
  4. 2026-08-25 12:22 UTCVendor advisory
  5. 2026-08-23 00:19 UTCEPSS rescore
  6. 2026-08-21 23:49 UTCEPSS rescore
  7. 2026-08-21 13:22 UTCEG score recompute
  8. 2026-08-21 13:22 UTCVendor advisory
  9. 2026-08-21 12:32 UTCEG score recompute
  10. 2026-08-21 12:32 UTCVendor advisory
  11. 2026-08-20 22:55 UTCEPSS rescore
  12. 2026-08-20 13:59 UTCEG score recompute
  13. 2026-08-20 13:59 UTCVendor advisory
  14. 2026-08-20 12:45 UTCEG score recompute
  15. 2026-08-20 12:45 UTCVendor advisory
  16. 2026-08-19 17:03 UTCEPSS rescore
  17. 2026-08-18 13:48 UTCEPSS rescore
  18. 2026-08-17 13:47 UTCEPSS rescore
  19. 2026-08-16 14:56 UTCEPSS rescore
  20. 2026-08-16 08:24 UTCEG score recompute
  21. 2026-08-16 08:24 UTCVendor advisory
  22. 2026-08-16 02:14 UTCEPSS rescore
  23. 2026-08-15 01:30 UTCEPSS rescore
  24. 2026-08-14 05:33 UTCEG score recompute
  25. 2026-08-14 05:33 UTCVendor advisory
  26. 2026-08-13 22:00 UTCEPSS rescore
  27. 2026-08-12 19:47 UTCEG score recompute
  28. 2026-08-12 19:47 UTCVendor advisory
  29. 2026-08-12 13:50 UTCEPSS rescore
  30. 2026-08-11 04:30 UTCEG score recompute
  31. 2026-08-11 04:30 UTCVendor advisory
  32. 2026-08-11 00:00 UTCEPSS rescore
  33. 2026-08-10 04:46 UTCEG score recompute
  34. 2026-08-10 04:46 UTCVendor advisory
  35. 2026-08-09 13:46 UTCEPSS rescore
  36. 2026-08-09 05:03 UTCEG score recompute
  37. 2026-08-09 05:03 UTCVendor advisory
  38. 2026-08-08 16:37 UTCEPSS rescore
  39. 2026-08-07 15:07 UTCEG score recompute
  40. 2026-08-07 15:07 UTCVendor advisory
  41. 2026-08-06 13:46 UTCEPSS rescore
  42. 2026-08-06 00:08 UTCEG score recompute
  43. 2026-08-06 00:08 UTCVendor advisory
  44. 2026-08-05 19:17 UTCEPSS rescore
  45. 2026-08-04 15:10 UTCEPSS rescore
  46. 2026-08-04 10:38 UTCEPSS rescore
  47. 2026-08-03 22:28 UTCEG score recompute
  48. 2026-08-03 22:28 UTCVendor advisory
  49. 2026-08-03 10:36 UTCEPSS rescore
  50. 2026-08-02 14:24 UTCEG score recompute
  51. 2026-08-02 14:24 UTCVendor advisory
  52. 2026-08-02 02:27 UTCEPSS rescore
  53. 2026-08-01 04:16 UTCEPSS rescore
  54. 2026-07-30 16:28 UTCEPSS rescore
  55. 2026-07-30 01:30 UTCEPSS rescore
  56. 2026-07-27 14:13 UTCEPSS rescore
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  65. 2026-07-23 03:09 UTCEG score recompute
  66. 2026-07-22 14:08 UTCEPSS rescore
  67. 2026-07-21 15:24 UTCEPSS rescore
  68. 2026-07-20 17:08 UTCEPSS rescore
  69. 2026-07-19 14:31 UTCEPSS rescore
  70. 2026-07-19 02:29 UTCEPSS rescore
  71. 2026-07-18 10:04 UTCEPSS rescore
  72. 2026-07-17 02:24 UTCOSV refresh
  73. 2026-07-16 17:03 UTCEPSS rescore
  74. 2026-07-15 16:57 UTCEPSS rescore
  75. 2026-07-15 16:57 UTCEPSS rescore

Frequently asked(5)

What is CVE-2026-34756?
CVE-2026-34756 is a medium vulnerability published on April 6, 2026. 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…
When was CVE-2026-34756 disclosed?
CVE-2026-34756 was first published in the National Vulnerability Database on April 6, 2026, with the most recent update on August 25, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-34756 actively exploited?
CVE-2026-34756 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 63.9% of all scored CVEs.
What is the CVSS score of CVE-2026-34756?
CVE-2026-34756 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2026-34756?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-34756, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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