Vulnerability in Role Deletion on PyPI

An exploitable vulnerability in the mechanisms for deleting roles on PyPI was discovered by a security researcher, which would allow an attacker to remove roles for projects not under their control.

  • Disclosure date: 2021-07-26 (Reported via security policy on
  • Disclosed by: RyotaK
  • Bounty awarded to discloser: $1,000 USD for multiple reports in 2021-07


PyPI has two types of permissions for users relative to projects: Owner and Maintainer. Permissions are stored by mapping a user ID to a project ID, with a permission, as a role. Each role has a unique ID.

PyPI users have the ability to remove roles for the projects they have the Owner role for. This is done via a web form by POST-ing the role ID to an endpoint dedicated to deleting roles.

This endpoint is guarded by a permissions check to ensure the current user has the Owner role on the current project. However, when querying for the role by ID, the query was missing a check that the current project matches the project the role is associated with.

This would enable any user to delete any role if they were able to procure a valid role ID.


Role IDs are represented on PyPI as UUIDs, and are therefore pseudo-random and not enumerable. In addition, role IDs for a given project are only exposed to any user with the Owner role on that project (via the same webform for deleting roles).

Given this, the PyPI administrators determined that it would not be possible for an attacker to acquire a role ID that they didn’t already have the ability to delete, and that any successful exploitation of this vulnerability would require a high volume of requests in attempt to brute force a role ID. In addition, any successful exploitation would only have the ability to remove a random role ID, and not a role for a specific user or project.


This vulnerability was fixed in via by adding a filter on the current project to the query for the role.


The PyPI administrators analyzed incidences of high-volume traffic to the role deletion endpoint, and found two days where the quantity of requests to this endpoint were far above average (>200 requests per day). The PyPI administrators analyzed all role deletions on these days and found them to be legitimate bulk removals of roles.


  • 2018-01-22: “Role management” feature added in (PR #2705)
  • 2021-07-26: Issue reported by RyotaK following guidelines in security policy on
  • 2021-07-27 (+1days): Fix is implemented and deployed in commit 7605be