---
schema_version: '1.0'
id: security-20260724-819d64
url: https://osv.dev/vulnerability/PYSEC-2026-3479
url_hash: 819d647c5bbf451af0f7c9578e973d144ecb8b602480f0468851626e3a8250f9
canonical_url: https://osv.dev/vulnerability/PYSEC-2026-3479
source: osv:pypa
category: security/library
category_raw: cve/library
region: null
tags:
- cve
- CVE-2026-59822
- PYSEC-2026-3479
- severity:CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N
- litellm
- PyPI
lang: en
published_at: '2026-07-23T11:41:48Z'
fetched_at: '2026-07-24T07:01:54.517941Z'
updated_at: '2026-07-24T07:02:21Z'
status: published
content_hash: 0dce5ce242956c00c43e1b9d065aff8f4701a87d034813941b1970eebd590eeb
content_changed_at: null
license_note: full
summary: 'LiteLLM: MCP Authentication Bypass via OAuth2 Passthrough Fallback'
summary_source: rss
summary_en: 'LiteLLM: MCP Authentication Bypass via OAuth2 Passthrough Fallback'
entities:
- name: CVE-2026-44243
  type: data
- name: MCP
  type: concept
- name: Herme's Dashboard Basic Authentication User
  type: person
key_facts: []
related: []
related_auto:
- name: Herme's Dashboard Basic Authentication Password
  type: person
  weight: 2.0
- name: 本人・法人認証
  type: UNKNOWN
  weight: 1.0
- name: 監査ログ
  type: UNKNOWN
  weight: 1.0
title: 'CVE-2026-59822: LiteLLM: MCP Authentication Bypass via OAuth2 Passthrough
  Fallback'
---

# CVE-2026-59822: LiteLLM: MCP Authentication Bypass via OAuth2 Passthrough Fallback

## TL;DR
LiteLLM: MCP Authentication Bypass via OAuth2 Passthrough Fallback

## Key Points
- cve / CVE-2026-59822 / PYSEC-2026-3479 / severity:CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N / litellm / PyPI

## Details
**Severity:** CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N
**Advisory:** PYSEC-2026-3479 (CVE-2026-59822)

**Affected (your watchlist):**
- `PyPI:litellm` 1.72.6.post2 → fixed in 1.84.0 [docker/docker-strands]

**Details:**
### Impact

LiteLLM's MCP Streamable HTTP endpoint could allow an unauthenticated attacker to establish an authenticated MCP session using an arbitrary Bearer token.

The MCP auth handler supported OAuth2 passthrough for upstream MCP servers, but the fallback path could replace failed LiteLLM key validation with an empty `UserAPIKeyAuth()` object. This allowed requests with a fabricated `Authorization` header to reach MCP tooling without a valid LiteLLM key.

An attacker could use this to list and call configured MCP tools and access connected services exposed through MCP.

### Patches

The issue is fixed in `1.84.0`.

We recommend upgrading to `1.84.0` or later.

### Workarounds

If upgrading is not immediately possible, disable MCP routes or block access to `/mcp/` and related MCP endpoints at your reverse proxy or API gateway.

### References

* [v1.84.0](https://github.com/BerriAI/litellm/releases/tag/v1.84.0)

**References:**
- https://github.com/BerriAI/litellm/security/advisories/GHSA-7488-6r32-c95q
- https://nvd.nist.gov/vuln/detail/CVE-2026-59822
- https://github.com/BerriAI/litellm/pull/26463
- https://github.com/BerriAI/litellm/commit/73869f0faf7d11ee21adcb5f91b8c33a340b6c2c
- https://github.com/BerriAI/litellm
- https://github.com/BerriAI/litellm/releases/tag/v1.84.0
- https://pypi.org/project/litellm
- https://github.com/advisories/GHSA-7488-6r32-c95q

_Data: OSV.dev (upstream: pypa) — https://osv.dev/vulnerability/PYSEC-2026-3479_

## Source
元記事: [CVE-2026-59822: LiteLLM: MCP Authentication Bypass via OAuth2 Passthrough Fallback](https://osv.dev/vulnerability/PYSEC-2026-3479) — published 2026-07-23T11:41:48Z