CVE-2026-119446: Session fixation in the CLI login flow allows an unauthenticated attacker to obtain a user's API token
Session Fixation vulnerability in the CLI login flow in nerves-hub nerveshubweb allows an unauthenticated attacker to obtain an API token for another user's account via a crafted login link. Starting a CLI login with POST /api/auth/clisession needs no authentication and returns a polling token, a confirmation URL that carries that token, and a confirmation code. When a signed-in user opens that URL and clicks Confirm, NervesHub.Accounts.verifyclisessiontoken/2 creates an API token for the user's account and stores it on the login, and the next poll of GET /api/auth/clisession/<token> returns it to whoever started the login.
The confirmation code is only displayed and is never compared with anything, so it cannot show that the person confirming is the one who started the login. The confirm form carries a CSRF token and the page cannot be framed, so the attacker has to persuade the user to open the link and click the button themselves.
This issue affects nerveshub: from 2.5.0 before 2.5.3.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
nerves_hubto a version that resolves this vulnerability.Fixed in 2.5.3 - Operational
After upgrading, review API tokens on the account page and delete any unrecognized tokens; upgrading does not revoke tokens already handed out.
Event History
Frequently Asked Questions
What does an attacker need to exploit this issue?
The attacker needs to start an unauthenticated CLI login, obtain its confirmation URL, and persuade a signed-in user to open that crafted URL and click Confirm. The attacker does not need the victim's credentials, but cannot complete the confirmation through framing because the page cannot be framed and the form uses a CSRF token.
Who can be affected?
A signed-in user who opens an attacker-provided CLI login confirmation link and confirms it can have an API token issued for their account. The attacker that initiated the associated CLI login can retrieve that token by polling the login endpoint.
Are unauthenticated endpoints involved?
Yes. POST /api/auth/cli_session can be used without authentication to create the CLI login session and obtain the polling token and confirmation URL. The confirmation code does not prevent the attack because it is displayed but never validated against the person who started the login.
Which versions are affected?
The issue affects nerves_hub versions from 2.5.0 up to, but not including, 2.5.3.