CVE-2026-66885 Livebook Teams identity callback lacks state binding, allowing login CSRF

Medium 6.8 Published 5 Aug 2026 Updated 6 Aug 2026

Attackers can force victims into sessions bound to attacker identities, exposing victim data and attributing work to the attacker.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Over the internet
Victim action needed: A user has to click or open something
Fix: Available

What is CVE-2026-66885?

CVE-2026-66885 is a medium-severity vulnerability in livebook-dev livebook, published on 5 Aug 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

Official description

Cross-Site Request Forgery (CSRF) vulnerability in livebook-dev livebook allows an attacker to authenticate a victim's browser session under the attacker's own Livebook Teams identity.

When Livebook is configured to use Livebook Teams for identity, Livebook.ZTA.LivebookTeams.handle_request/4 in lib/livebook/zta/livebook_teams.ex handles the OAuth-style callback carrying a teams_identity marker and a code parameter. The clause exchanges that code for an access token and writes the token into the browser session without verifying any value that ties the callback to the browser session that started the login. No state or nonce is generated when the flow is initiated: Livebook.Teams.Requests.create_auth_request/1 in lib/livebook/teams/requests.ex sends an empty request body, so no per-attempt value is ever registered, and the callback clause has nothing to compare against.

An attacker who holds membership in the same Livebook Teams organisation as the target instance can therefore begin the login flow themselves, retain the resulting authorization code without redeeming it, and induce a victim to open a crafted URL carrying that code. The victim's browser completes the exchange and the resulting session is bound to the attacker's identity rather than the victim's. The victim is not required to hold any particular privilege, and no credential belonging to the victim is involved. The vulnerability does not allow the attacker to authenticate as the victim.

The consequence is that a user believes they are working in their own authenticated session while they are in fact operating as another identity. Work performed in that session is attributed to the attacker's account, and secrets, uploaded data, or notebook results the victim produces are exposed to the attacker rather than kept in the victim's own account. The authorization code must be redeemed within a short window after the login flow begins, which constrains the timing of the attack but not its feasibility.

This issue affects livebook: from 0.15.0 before 0.18.7 and from 0.19.0 before 0.19.9.

Weakness: CWE-352

Which versions are affected by CVE-2026-66885?

1 open source package ship an affected version, including livebook. It affects 1 product.

Package	Affected	Fixed in
`livebook` Hex	From `0.15.0`	`0.18.7, 0.19.9`

Products include Livebook Livebook.

How do I fix CVE-2026-66885?

Upgrade livebook to a fixed version for your release line: 0.18.7 or 0.19.9.

Is CVE-2026-66885 being exploited?

There is no known exploitation of CVE-2026-66885 in the wild and no public exploit code.

Sources

Also known as EEF-CVE-2026-66885, GHSA-pvvw-28fw-c6fg.