Audiobookshelf Auth Bypass

Vulnerable Application

Audiobookshelf is a self-hosted audiobook and podcast server. Versions 2.17.0 through 2.19.0 are affected by CVE-2025-25205, an unauthenticated authentication bypass.

The authentication middleware (server/Auth.js) decides whether a GET request may skip authentication by testing unanchored regular expressions (/\/api\/items\/[^/]+\/cover/ and /\/api\/authors\/[^/]+\/image/) against req.originalUrl, which includes the query string, instead of the normalized req.path. An unauthenticated request to a protected API endpoint that appends a query value containing one of those substrings — for example /api/libraries?r=/api/items/1/cover — satisfies the "auth not needed" check while Express still routes it to the protected handler. Depending on the endpoint this leaks protected data, or returns an HTTP 500 where the handler dereferences the now-undefined user object. The issue was fixed in 2.19.1 by anchoring the patterns and matching req.path.

This module fingerprints the server and version through the unauthenticated /status endpoint, then performs a differential check against the protected /api/libraries endpoint: a baseline request that a server normally rejects with HTTP 401, and a bypass request carrying the whitelisted substring. On a vulnerable server the auth check is skipped and the bypass request is processed (HTTP 200, or 500 because the handler runs without a user); a patched server returns 401 to both. The 500 is request-level and the server stays up. The module deliberately avoids endpoints such as /api/users that crash the server process (the denial-of-service half of this CVE).

Setup with Docker

A vulnerable instance can be run with the official image pinned to a vulnerable tag:

docker run -d --name abs-vuln -p 13378:80 ghcr.io/advplyr/audiobookshelf:2.19.0

Browse to http://127.0.0.1:13378 and complete the initial root-user setup. This is required: before initialization the server returns HTTP 500 to the protected API. After setup, the bypass request to /api/libraries returns HTTP 500 on a vulnerable server (the auth check is skipped and the handler runs without a user), which the module treats as confirmation; the same request returns HTTP 401 on a patched server.

To confirm the true-negative behavior, run a patched instance on a different port and complete its setup the same way:

docker run -d --name abs-patched -p 13379:80 ghcr.io/advplyr/audiobookshelf:2.19.1

Verification Steps

1. Start a vulnerable Audiobookshelf instance and complete its setup (see Setup with Docker)
2. Start msfconsole
3. Do: use auxiliary/scanner/http/audiobookshelf_auth_bypass
4. Do: set RHOSTS <target>
5. Do: set RPORT 13378
6. Do: run
7. The module reports the detected version and confirms the authentication bypass

Options

TARGETURI

The base path to the Audiobookshelf application. Defaults to /. Set this when Audiobookshelf is served from a sub-path behind a reverse proxy.

Scenarios

Audiobookshelf 2.19.0 (vulnerable)

msf6 > use auxiliary/scanner/http/audiobookshelf_auth_bypass
msf6 auxiliary(scanner/http/audiobookshelf_auth_bypass) > set RHOSTS 127.0.0.1
RHOSTS => 127.0.0.1
msf6 auxiliary(scanner/http/audiobookshelf_auth_bypass) > set RPORT 13378
RPORT => 13378
msf6 auxiliary(scanner/http/audiobookshelf_auth_bypass) > run

[+] 127.0.0.1:13378       - Audiobookshelf 2.19.0 - unauthenticated API authentication bypass confirmed (CVE-2025-25205)
[*] Scanned 1 of 1 hosts (100% complete)
[*] Auxiliary module execution completed

Audiobookshelf 2.19.1 (patched, true-negative)

msf6 auxiliary(scanner/http/audiobookshelf_auth_bypass) > set RPORT 13379
RPORT => 13379
msf6 auxiliary(scanner/http/audiobookshelf_auth_bypass) > run

[*] 127.0.0.1:13379       - Audiobookshelf 2.19.1 - not vulnerable (authentication enforced)
[*] Scanned 1 of 1 hosts (100% complete)
[*] Auxiliary module execution completed