{"id":"CVE-2026-52804","aliases":["GHSA-4565-r4x7-hg8j","GO-2026-5110"],"url":"https://o3.security/vulnerability/CVE-2026-52804","summary":"Gogs: Privilege Escalation via Collaboration Access Mode Validation","details":"## Summary\n\nA repository admin collaborator can escalate their privileges to owner-level access by exploiting an off-by-one error in the `ChangeCollaborationAccessMode` function.\n\n## Vulnerable Code\n\nIn `internal/database/repo_collaboration.go`, line 129:\n\n```go\nfunc (r *Repository) ChangeCollaborationAccessMode(userID int64, mode AccessMode) error {\n    // Discard invalid input\n    if mode <= AccessModeNone || mode > AccessModeOwner {\n        return nil\n    }\n```\n\n`AccessModeOwner` has value 4. The check `mode > AccessModeOwner` evaluates to `4 > 4 = false`, allowing `AccessModeOwner` to pass through. The correct check should be `mode >= AccessModeOwner`.\n\nThe web route at `internal/route/repo/setting.go:413-416` takes the mode as a raw integer from query parameters:\n\n```go\nfunc ChangeCollaborationAccessMode(c *context.Context) {\n    if err := c.Repo.Repository.ChangeCollaborationAccessMode(\n        c.QueryInt64(\"uid\"),\n        database.AccessMode(c.QueryInt(\"mode\"))); err != nil {\n```\n\nThis allows an admin collaborator to POST `mode=4` and escalate to owner.\n\n## Impact\n\nA repository admin collaborator (AccessModeAdmin = 3) can escalate to owner-level access (AccessModeOwner = 4), gaining the ability to:\n- **Delete the repository**\n- **Transfer repository ownership** to another user\n- **Erase wiki data**\n- Perform all other owner-only operations\n\nThe `access` table is also updated (line 181), so the escalated permissions persist across sessions.\n\n## Contrast\n\nThe API route at `internal/route/api/v1/repo_collaborators.go:46` uses `ParseAccessMode()` which only returns Read, Write, or Admin - never Owner. The API endpoint is not affected.\n\n## Steps to Reproduce\n\n1. User A creates a private repository\n2. User A adds User B as a collaborator with **Admin** access (mode=3)\n3. User B logs in and navigates to the repository settings collaboration page\n4. User B sends a POST request:\n   ```\n   POST /{owner}/{repo}/settings/collaboration/access_mode?uid={B_uid}&mode=4\n   ```\n5. User B now has **Owner** access - the \"Danger Zone\" section appears with \"Delete This Repository\" and \"Transfer Ownership\" buttons\n\n## Suggested Fix\n\nChange the validation in `internal/database/repo_collaboration.go` line 129 from:\n```go\nif mode <= AccessModeNone || mode > AccessModeOwner {\n```\nto:\n```go\nif mode <= AccessModeNone || mode >= AccessModeOwner {\n```","published":"2026-06-24T20:20:26.848Z","modified":"2026-10-21T02:58:27.596658387Z","cvss":null,"epss":{"score":0.00499,"percentile":0.41558,"asOf":"2026-09-16"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"gogs.io/gogs","fixedVersion":"0.14.3"}],"fix":{"url":"https://github.com/gogs/gogs/commit/1fdc9cc28e159135cfa4d6b11ecd5daa0f8ce22b","label":"gogs/gogs@1fdc9cc"},"references":[{"type":"WEB","url":"https://github.com/gogs/gogs/releases/tag/v0.14.3"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/52xxx/CVE-2026-52804.json"},{"type":"ADVISORY","url":"https://github.com/gogs/gogs/security/advisories/GHSA-4565-r4x7-hg8j"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-52804"},{"type":"FIX","url":"https://github.com/gogs/gogs/commit/1fdc9cc28e159135cfa4d6b11ecd5daa0f8ce22b"},{"type":"FIX","url":"https://github.com/gogs/gogs/pull/8227"},{"type":"PACKAGE","url":"https://github.com/gogs/gogs"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-21T02:58:27.596658387Z"}}