{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.26.1"
      },
      "package": {
        "ecosystem": "Go",
        "name": "code.gitea.io/gitea"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.26.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-28699"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-284",
      "CWE-863"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-16T23:40:34Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Summary\n\nGitea fails to enforce OAuth2 access token scopes when the token is submitted via HTTP Basic authentication instead of a Bearer token. An OAuth2 application granted only `read:user` can use the same token as `Authorization: Basic base64(\u003ctoken\u003e:x-oauth-basic)` and perform write actions, including modifying profiles, adding email addresses, creating repositories, and deleting repositories as the authorizing user.\n\n### Details\n\n**Root cause:** `services/auth/basic.go` accepts OAuth2 access tokens through the Basic auth path but does not store the token scope in the request context:\n\n```go\n// services/auth/basic.go\nif uid != 0 {\n    store.GetData()[\"LoginMethod\"] = OAuth2TokenMethodName\n    store.GetData()[\"IsApiToken\"] = true   // scope is NOT set\n    return u, nil\n}\n```\n\nThe scope enforcement middleware in `routers/api/v1/api.go` exits early when `ApiTokenScope` is absent:\n\n```go\n// routers/api/v1/api.go \u2014 tokenRequiresScopes\nscope, scopeExists := ctx.Data[\"ApiTokenScope\"].(auth_model.AccessTokenScope)\nif ctx.Data[\"IsApiToken\"] != true || !scopeExists {\n    return   //\u003c- exits without checking scope, all actions permitted\n}\n```\n\nWhen a token arrives via Bearer, `ApiTokenScope` is populated and scope checks apply normally. When the same token arrives via Basic auth, `ApiTokenScope` is never set, so `tokenRequiresScopes` returns immediately and no scope is enforced.\n\n**Suggested fix:** When an OAuth2 access token is accepted in `services/auth/basic.go`, populate `ApiTokenScope` in the request context identically to the Bearer-token OAuth2 path.\n\n### PoC\n\n1. Create an OAuth2 application in Gitea.\n2. Authorize it as a normal user with scope `read:user` only.\n3. Take the resulting access token and call a write endpoint both ways:\n\n**Bearer | correctly blocked:**\n```\nAuthorization: Bearer \u003ctoken\u003e\nPATCH /api/v1/user/settings  -\u003e  403 Forbidden\n```\n\n**Basic | bypass:**\n```\nAuthorization: Basic base64(\u003ctoken\u003e:x-oauth-basic)\nPATCH /api/v1/user/settings  -\u003e  200 OK\n```\n\n**All verified bypass endpoints using a `read:user`-only token:**\n\n| Endpoint | Bearer | Basic |\n|---|---|---|\n| `PATCH /api/v1/user/settings` | 403 | 200 |\n| `POST /api/v1/user/emails` | 403 | 200 |\n| `POST /api/v1/user/repos` | 403 | 200 |\n| `PATCH /api/v1/repos/{owner}/{repo}` | 403 | 200 |\n| `DELETE /api/v1/repos/{owner}/{repo}` | 403 | 200 |\n\nThe bypass respects the user\u0027s normal repository permissions, it does not grant access to repositories the user cannot otherwise reach, and does not escalate to admin.\n\n### Impact\n\nAny OAuth2 application with any restricted scope can silently operate beyond its granted permissions by switching from Bearer to Basic auth. An attacker who obtains a token (e.g. via a malicious OAuth2 app a user authorized) can:\n\n- Modify the victim\u0027s profile and settings\n- Add attacker-controlled email addresses to the victim\u0027s account\n- Create repositories as the victim\n- Modify or delete the victim\u0027s private repositories\n\nThe entire OAuth2 scope system is effectively bypassed for any token submitted via Basic auth.",
  "id": "GHSA-9r5x-wg6m-x2rc",
  "modified": "2026-06-16T23:40:34Z",
  "published": "2026-06-16T23:40:34Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/go-gitea/gitea/security/advisories/GHSA-9r5x-wg6m-x2rc"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/go-gitea/gitea"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Gitea: OAuth2 access token scope enforcement bypass via HTTP Basic authentication"
}