CVE-2026-121880 | BDVDB-2026-401174 Detail
Posit Software, PBCPosit Workbench
Description#
Authorization bypass through user-controlled key in the localhost port-proxy (/p/<token>/) in Posit Software, PBC RStudio Server and Posit Workbench before 2026.08.0 allows remote authenticated users to reach web applications and other services bound to 127.0.0.1 under a different user's session, and to view their live rendered content and data, via a proxy URL constructed from the attacker's own port token for an arbitrary port number. The port token is a documented obfuscation measure and not an authorization boundary, and the proxy does not verify that the requested port belongs to the requesting user's session. NOTE: exploitation requires an authenticated account on the same multi-user server and a target service listening on localhost at the time of access. Impact may be greater on hosts that co-locate additional privileged localhost services, and the bypass is not prevented by allow-shell=false; no setting restricts the port-proxy without disabling all application proxying.
Impact#
Information disclosure: an authenticated user can view another user's running application and the data it renders. Where other network services are bound to localhost on the same host, those services may also become reachable through the proxy, and the potential impact in those deployments depends on what is running and how it is configured.
Weaknesses#
References#
Exploit#
No public exploit known
History#
- Version 1Record published in the CVE List.