UnratedPublic exploit

Authentication Bypass in vLLM OpenAI API AuthenticationMiddleware

IdentifiersCVE-2026-48746CWE-288

CVE-2026-48746 is a critical authentication bypass vulnerability in vLLM, an inference and serving engine for large language models. It affects vLLM versions 0.3.0 through 0.21.x, and is fixed in 0.22.0. The flaw arises from behavior in ASGI web servers combined with Starlette’s trust in those web servers during URL reconstruction from the Host header, which allows bypass of the OpenAI API AuthenticationMiddleware. As a result, a remote attacker can access and use the OpenAI-compatible API without supplying the configured VLLM_API_KEY or the --api-key value.

For your environment

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation allows unauthenticated remote access to the vLLM OpenAI-compatible API on affected deployments. This can permit unauthorized model inference requests and any other API operations gated only by the API key mechanism. The provided context rates the issue Critical with CVSS 3.1 score 9.1 and indicates high confidentiality, integrity, and availability impact.

Mitigation

If you can’t patch tonight, do this now.

Until patching is completed, do not expose affected vLLM instances directly to untrusted networks. Place vLLM behind an RFC-conforming web server such as nginx that properly validates or normalizes the Host header, and restrict network exposure to trusted clients only.

Remediation

Patch, then assume compromise.

Upgrade vLLM to version 0.22.0 or later, where the vulnerability is fixed. After upgrading, verify that API key authentication is enforced as expected for the OpenAI-compatible API.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType

Vllm-ProjectVllmapplication

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

5 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

5 SOURCESView more in app

cvefeed high severityNews

Jun 22, 2026

CVE-2026-48746 - vLLM: OpenAI auth bypass

An authentication bypass vulnerability in vLLM's OpenAI API AuthenticationMiddleware that allows remote unauthenticated use of the API without the configured API key.

What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.

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Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity4

Community discussion across Reddit, Mastodon, and other social sources.

EXTERNAL REFERENCES

MITRE CVE

cve.org · CVE-2026-48746

NVD

nvd.nist.gov/vuln/detail/CVE-2026-48746

MITRE CWE · CWE-288

cwe.mitre.org