CVE-2023-51442

EUVD-2023-3317 · Published Dec 19, 2023

Authentication bypass vulnerability in navidrome's subsonic endpoint

Summary

A security vulnerability has been identified in navidrome's subsonic endpoint, allowing for authentication bypass. This exploit enables unauthorized access to any known account by utilizing a JSON Web Token (JWT) signed with the key "not so secret".

The vulnerability can only be exploited on instances that have never been restarted.

Details

Navidrome supports an extension to the subsonic authentication scheme, where a JWT can be provided using a jwt query parameter instead of the traditional password or token and salt (corresponding to resp. the p or t and s query parameters).

During the first initialization, navidrome generates a random key that is then used by the authentication module to validate JWTs before extracting the username from the sub claim. If for some reason the key cannot be retrieved by the initialization code, a hardcoded value is used instead: "not so secret".

A bug in the order of operations during navidrome startup results in the authentication module initializing before the module responsible for generating and persisting the random key. As a consequence, the authentication module falls back to using the hardcoded value, which remains in use until the instance gets restarted. Additionally, an error that was meant to be logged when the fallback value is used does not get logged due to another bug, preventing the operator from becoming aware of the issue.

The flaw allows the creation of a JWT with the sub claim set to any existing user on the server, signed with the key "not so secret", which can then be used to authenticate against the subsonic endpoint with the chosen user's privileges.

After navidrome is restarted, the random key generated during the previous startup is loaded and the flaw becomes inexploitable.

PoC

Generate a JWT token with the subject "admin", and key "not so secret" (e.g. online on: http://jwtbuilder.jamiekurtz.com; the other parameters can be left in, it doesn't seem that navidrome validates anything). In a shell, assign the token to the variable JWT (for the curl commands below).

$ podman run -d --name navidrome -p 127.0.0.1:4533:4533 -e ND_DEVAUTOCREATEADMINPASSWORD=password docker.io/deluan/navidrome:0.50.1
$ curl "http://localhost:4533/rest/ping.view?c=dummy&v=1&u=admin&jwt=$JWT"
<subsonic-response xmlns="http://subsonic.org/restapi" status="ok" version="1.16.1" type="navidrome" serverVersion="0.50.1 (f69c27d1)" openSubsonic="true"></subsonic-response>

The ND_DEVAUTOCREATEADMINPASSWORD parameter does not influence the bypass, it also works if the admin or extra users are created manually after starting navidrome.

Restarting navidrome prevents the bypass:

$ podman restart navidrome
$ curl "http://localhost:4533/rest/ping.view?c=dummy&v=1&u=admin&jwt=$JWT"
<subsonic-response xmlns="http://subsonic.org/restapi" status="failed" version="1.16.1" type="navidrome" serverVersion="0.50.1 (f69c27d1)" openSubsonic="true"><error code="40" message="Wrong username or password"></error></subsonic-response>

Impact

This authentication bypass vulnerability potentially affects all instances that don't protect the subsonic endpoint /rest/, which is expected to be most instances in a standard deployment, and most instances in the reverse proxy setup too (as the documentation mentions to leave that endpoint unprotected).

The impact is limited by the fact that the flaw becomes inexploitable after a first restart, and the attacker needs to know the username of existing users on the instance.

For each known user, the attacker could mess with (create/delete/change) playlists, bookmarks, media annotations, shares (which are currently global) and radios. He is also able to get the user's email address (which is PII) with the getUser operation. And lastly he can use the media retrieval operations which could potentially affect the availability of the system.

Technologies

Navidrome Navidrome

Weaknesses

CWE-287

CVSS scores

v3.18.6CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H

MITRE ATT&CK

Inferred

Where this vulnerability fits in an attack

ReconImpact

Initial Access

T1190Exploit Public-Facing Application

References

Potentially impacted assets

See if this affects your attack surface

Latest trending attack

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Google Brotli decoder - Remote Code Execution via compressed requests (Exploitation Check)

This control is the second step of the Patrowl response to CVE-2026-111497 (Node2Shell). It complements the first control of 22 October 2026, which focused on the Node.js runtime, and does not replace it. Why a second control CVE-2026-111497 is an out-of-bounds write in the Google Brotli decoder, the library that decompresses Brotli ("br") data. It was first published as a Node.js vulnerability, because Node.js bundles this decoder. Later publications showed that the flaw is in the library itself. Every product that embeds an affected version of the decoder is concerned, whatever its language or vendor. A public proof of concept demonstrates code execution. Any server that decompresses request bodies sent with "Content-Encoding: br" exposes the decoder to unauthenticated attackers. Known cases include Express 5 and NestJS 11 on Node.js, Koa and Fastify setups, Bun, Envoy and Istio with request decompression enabled, and any application or reverse proxy that decodes Brotli request bodies with an affected library. The flaw also works in the other direction. A malicious server can compromise an unpatched client that decodes a Brotli response, for example Node.js fetch(), Python clients (requests, httpx, aiohttp, Scrapy) with the Brotli or brotlicffi package, or libcurl builds with Brotli support. What this control checks Patrowl sends small, valid Brotli-compressed requests to each asset and observes whether the server decodes them. The check does not depend on the technology: it detects the behaviour, whatever the stack behind it. These requests are what any legitimate client could send. They never reach the vulnerable code path and cannot affect the availability of the service. How to read the result Potentially impacted means the asset decodes Brotli request bodies: the attack surface is exposed. It does not confirm that the asset is vulnerable. The version of the Brotli decoder in use is not visible from the outside. This check covers applications that parse request bodies on their root path. A Not impacted result does not rule out exposure on other routes, nor on the client side. Checking the versions on the servers remains the only exhaustive verification. Two situations are possible. When the decoding is done by your own application or reverse proxy, identify the component and update it. If an update is not possible right away, reject requests with "Content-Encoding: br" at the reverse proxy or WAF. When the asset is hosted on a managed platform or behind a CDN (for example Platform.sh, Upsun or Fastly), the decoding may be done by the provider's edge router, in front of your application. You cannot patch it yourself, but this router handles all the traffic of your site. Ask your provider to confirm that its edge components are patched against CVE-2026-111497. Assets hosted on a managed platform or behind a CDN carry the tag "paas: platform.sh" or "cdn: fastly" in the asset view: for these assets, the Brotli decoding is done by the provider's edge router, in front of your application, and only the provider can patch it. Affected and fixed versions Google Brotli 1.0.3 to 1.2.0 are affected, fixed in 1.0.10, 1.1.1 and 1.2.1. Fixed releases of the main products embedding it: Node.js 22.23.4, 24.22.1 and 26.12.1 (end-of-life lines 20.x and older and 25.x receive no fix), Bun 1.4.4, Envoy 1.37.8, 1.38.6, 1.39.3 and 1.40.0, Istio 1.29.9, 1.30.6 and 1.31.2, Python Brotli 1.2.1 and brotlicffi 1.2.1.0. Products that link against the system library depend on the Brotli package of the Linux distribution. Recommendations Update every component that embeds the Brotli decoder (only real fix). Start with the assets flagged by this control. Restart the processes after the update. Rebuild containers, single-executable applications and appliances that bundle an affected runtime or library. Reduce the exposure until the update is deployed. Reject requests with "Content-Encoding: br" at the reverse proxy, load balancer or WAF, case-insensitively and including lists such as "gzip, br". On Envoy and Istio, disable request decompression for Brotli. Contact your edge provider about the status of the pathing (Fastly / Plateform.sh) Review outbound calls. List the features that fetch content from servers you do not control, and patch the services that host them first.