Vulnerability · Published Sep 15, 2026 · Assigned by GitHub_M
CVE-2026-49446Cosmos: Authentication bypass via forward-auth header smuggling on Constellation tunnel in Cosmos-Server
Medium 6.1
In plain English
A medium-severity authentication bypass by spoofing in Cosmos-Server from azukaar. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 23% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/azukaar/cosmos-server | 0.22.19 | GHSA-2rx5-2g7j-2659 |
| Go | github.com/azukaar/cosmos-server | 0.22.19 | GO-2026-6123 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| azukaar | Cosmos-Server | < 0.22.19 |
Weakness: CWE-285, CWE-290 · Vector: CVSS:3.1/AV:A/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N