GHSA-268j-37xf-pp52 Gogs's write-level collaborators can mutate admin-only repository settings via API
SummaryThree API endpoints — `PATCH /api/v1/repos/:owner/:repo/issue-tracker`, `PATCH /api/v1/repos/:owner/:repo/wiki`, and `POST /api/v1/repos/:owner/:repo/mirror-sync` — are gated by `reqRepoWriter()` rather than `reqRepoAdmin()`. The equivalent operations in the web UI sit behind `reqRepoAdmin`, which requires `AccessMode >= AccessModeAdmin`. A write-level collaborator (who has `AccessMode == AccessModeWrite < AccessModeAdmin`) can therefore call these API endpoints directly to disable the native issue tracker or wiki, inject attacker-controlled external tracker/wiki URLs that redirect all repository visitors, or trigger mirror sync — none of which they are authorized to do.Severity**High** (CVSS 3.1: 7.1)`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L`**Attack Vector:** Network — the API endpoints are reachable over HTTP/S.**Attack Complexity:** Low — a single API call is sufficient; no chaining or race condition required.**Privileges Required:** Low — only write-level collaborator access to the targeted repository is needed. The attacker does not need repo-admin or site-admin privileges.**User Interaction:** None — the attacker acts unilaterally.**Scope:** Unchanged — the impact is contained to the targeted repository's settings and its visitors.**Confidentiality Impact:** None — the attacker does not read confidential data directly.**Integrity Impact:** High — the attacker permanently mutates repository configuration, including injecting an external URL that redirects all visitors who click the Issues or Wiki tabs to an attacker-controlled site.**Availability Impact:** Low — disabling the native issue tracker or wiki reduces the availability of those features for all repository participants.Affected component`internal/route/api/v1/api.go` — route registration (lines 365–367)`internal/route/api/v1/repo_repo.go` — `issueTracker()` (line 400), `wiki()` (line 437), `mirrorSync()` (line 463)CWE**CWE-863**: Incorrect Authorization**CWE-269**: Improper Privilege ManagementDescriptionThree admin-equivalent API endpoints are protected by write-level middleware`api.go:365-367` registers the three settings endpoints with `reqRepoWriter()`:`reqRepoWriter()` (defined at `api.go:131-138`) passes any user whose repository `AccessMode >= AccessModeWrite`:The handlers themselves perform no additional privilege check before mutating state:The `wiki()` handler (lines 437–461) follows the same pattern, writing `repo.ExternalWikiURL` directly and calling `UpdateRepository` with no admin gate.The web UI imposes a stricter admin requirement for the same operations`cmd/gogs/web.go:472` wraps the entire `/settings` subtree with `reqRepoAdmin`:`context.RequireRepoAdmin()` (defined at `context/repo.go:434-441`) requires `AccessMode >= AccessModeAdmin`:In the access mode hierarchy, `AccessModeWrite < AccessModeAdmin`. A write-level collaborator satisfies `reqRepoWriter()` but does not satisfy `RequireRepoAdmin()`. The API path provides the write-level collaborator with capabilities that the UI correctly withholds.Full execution chain**Attacker precondition**: Attacker is added as a repository collaborator with write access (`AccessMode == AccessModeWrite`).**API call**: `PATCH /api/v1/repos/OWNER/REPO/issue-tracker` with `Authorization: token WRITER_TOKEN` and body `{"enable_external_tracker":true,"external_tracker_url":"https://attacker.example/phish"}`.**Middleware**: `reqRepoWriter()` checks `c.Repo.IsWriter()` → `AccessMode >= AccessModeWrite` → passes.**Handler**: `issueTracker()` sets `repo.EnableExternalTracker = true` and `repo.ExternalTrackerURL = "https://attacker.example/phish"`, then calls `database.UpdateRepository(repo, false)`. No admin check occurs.**Impact**: All visitors to the repository who click the "Issues" tab are redirected to the attacker's server. The native issue tracker is bypassed permanently until a repo admin reverses the change.Proof of ConceptImpactA write-level collaborator can permanently replace the native issue tracker with an external URL under attacker control, redirecting all repository visitors who follow the Issues link to a phishing or malware-serving page.The same redirect attack applies to the Wiki tab via the external wiki URL setting.Both redirects remain active until a repo admin or owner manually reverses the setting; the attacker has no way to be removed from having already made the change.Mirror sync can be triggered repeatedly, potentially causing unnecessary load on the upstream mirror source or consuming network resources.All three operations are silent — no notification is sent to repo admins when these settings change via the API.Recommended remediationOption 1: Change middleware to `reqRepoAdmin()` on all three endpoints (preferred)Replace `reqRepoWriter()` with `reqRepoAdmin()` at the route registration level. This is a one-line change per endpoint and aligns the API authorization with the web UI's established policy.Option 2: Add an explicit admin check inside the handlersAdd `c.Repo.IsAdmin()` checks at the top of `issueTracker()`, `wiki()`, and `mirrorSync()`. This is less preferred because it duplicates middleware logic in handler code, but it provides defense-in-depth if the route middleware is ever accidentally changed.CreditThis vulnerability was discovered and reported by [bugbunny.ai](https://bugbunny.ai).
CVSS v3.1 score: 7.1