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GHSA-66m4-5jjr-2rg5

MediumCVSS 6.8 / 10
Published Jul 21, 2026·Last modified Jul 21, 2026
Affected Components(0)

No affected components available

Description

Affected product

Gitea — services/repository/collaboration.go (DeleteCollaboration) + webhook delivery

Summary

When a collaborator with admin permission on a private repo creates a webhook, that webhook keeps firing after the collaborator's access is revoked. Gitea's revocation cleanup DeleteCollaboration removes the collaboration record, recalculates accesses, drops watches, and unassigns issues — but it does not remove or disable webhooks the user created, and webhook delivery never re-checks whether the creator still has repo access. The former collaborator therefore receives the full payload (issue/comment bodies, commit data) of all future repository events at their controlled endpoint, indefinitely and invisibly.

Affected code

  • services/repository/collaboration.go → DeleteCollaboration() — cleans watches/assignees only; no webhook cleanup.
  • Webhook delivery path — fires on repo events without re-validating the creator's current access.

Steps to reproduce

Using the provided reproduction materials:

  1. Attacker (admin collaborator) creates a webhook → revoke access.
  2. Control: GET /api/v1/repos/admin/wh-repo (attacker) → 404.
  3. GET .../hooks → webhook still active=true.
  4. Admin creates a new issue after revocation → the catcher receives action:"opened", issue.title:"CRITICAL SECRET: …", issue.body (sentinel private key), repository.private:true. (Runtime-confirmed on gitea/gitea:1.25.4. Catcher is an internal sentinel listener; the payload is a planted sentinel, not real data; nothing is sent to any external/metadata endpoint.)

Impact

Authenticated former admin-collaborator → ongoing real-time exfiltration of private content created after revocation; invisible to the owner; scope crosses from the application boundary to data the user should no longer access.

Suggested remediation

  1. On revocation, delete/disable webhooks created by the removed collaborator (or hand them to the owner).
  2. Re-validate the creator's current repo access before each webhook delivery.
  3. At minimum, warn admins on revocation if the user created webhooks.

Credit

Reported as part of an incomplete-patch / authorization-residue measurement study (responsible disclosure).

Risk Scores
Base Score
6.8

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs high-level or administrative privileges. No user interaction is needed for the attacker to exploit this vulnerability. The vulnerability can affect other systems as well, not just the initial system. There is a high impact on the confidentiality of the information.

Threat Intelligence
6.2

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
N/A

Probability that this vulnerability will be exploited in the wild within the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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Medium severity
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