CVE-2026-49446
Received Received - Intake

Security Bypass in Cosmos Self-Hosted Server

Publication date: 2026-09-15

Last updated on: 2026-09-15

Assigner: GitHub, Inc.

Description
Cosmos provides users the ability self-host a home server by acting as a secure gateway to your application, as well as a server manager. Prior to 0.22.19, tokenMiddleware in src/proxy/routerGen.go can return through the Constellation tunnel bypass before removing x-cosmos-user, x-cosmos-role, x-cosmos-user-role, and x-cosmos-mfa headers and before invoking AdminOnlyWithRedirect. An attacker with a valid x-cstln-auth API key for an enrolled device who reaches Cosmos through the Constellation Nebula tunnel can supply a chosen x-cosmos-user value to a route with AuthEnabled enabled when the upstream application trusts that forward-auth header. The request can bypass Cosmos JWT, password, MFA, and AdminOnly checks, allowing user impersonation and admin-tier reads or writes exposed by the proxied application. This issue is fixed in version 0.22.19.

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Meta Information

Published
2026-09-15
Last Modified
2026-09-15
Generated
2026-09-15
AI Q&A
2026-09-15
EPSS Evaluated
N/A
NVD
CVE-2026-49446
EUVD
EUVD-2026-78588

Affected Vendors & Products

Showing 3 associated CPEs
Vendor Product Version / Range
cosmos cosmos 0.22.19
azukaar cosmos-server 0.22.19
azukaar cosmos-server to 0.22.19 (exc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-285 The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action.
CWE-290 This attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks.

Attack-Flow Graph

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Executive Summary

This vulnerability allows an attacker with a valid API key to bypass authentication checks in Cosmos versions before 0.22.19. By exploiting the Constellation Nebula tunnel, the attacker can set a custom user header that bypasses Cosmos JWT, password, MFA, and admin checks. This enables user impersonation and unauthorized access to admin-tier functions in the proxied application.

Detection Guidance

Check Cosmos-Server logs for requests containing x-cosmos-user, x-cosmos-role, x-cosmos-user-role, or x-cosmos-mfa headers after authentication bypass attempts. Inspect network traffic for unauthorized admin-level requests via Constellation tunnel with valid x-cstln-auth keys.

Impact Analysis

If you use Cosmos versions before 0.22.19, an attacker could impersonate users or admins, access sensitive data, or perform unauthorized actions. This could lead to data breaches, unauthorized modifications, or loss of control over your server.

Compliance Impact

This vulnerability could lead to unauthorized access to personal or sensitive data, violating GDPR and HIPAA requirements for data protection and access controls. Non-compliance may result in legal penalties, fines, or reputational damage.

Mitigation Strategies

Upgrade Cosmos to version 0.22.19 or later to address the vulnerability. Ensure all enrolled devices using the Constellation tunnel are updated. Review and restrict access to routes with AuthEnabled to prevent unauthorized user impersonation.

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