CVE-2026-28699: Gitea Remote Code Execution Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-9r5x-wg6m-x2rc",
  "modified" : "2026-06-16T23:40:34Z",
  "published" : "2026-06-16T23:40:34Z",
  "aliases" : [ "CVE-2026-28699" ],
  "summary" : "Gitea: OAuth2 access token scope enforcement bypass via HTTP Basic authentication",
  "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(<token>: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 — tokenRequiresScopes\nscope, scopeExists := ctx.Data[\"ApiTokenScope\"].(auth_model.AccessTokenScope)\nif ctx.Data[\"IsApiToken\"] != true || !scopeExists {\n    return   //<- 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 <token>\nPATCH /api/v1/user/settings  ->  403 Forbidden\n```\n\n**Basic | bypass:**\n```\nAuthorization: Basic base64(<token>:x-oauth-basic)\nPATCH /api/v1/user/settings  ->  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's 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's profile and settings\n- Add attacker-controlled email addresses to the victim's account\n- Create repositories as the victim\n- Modify or delete the victim's private repositories\n\nThe entire OAuth2 scope system is effectively bypassed for any token submitted via Basic auth.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "code.gitea.io/gitea"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.26.2"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.26.1"
    }
  } ],
  "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"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-284", "CWE-863" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-16T23:40:34Z",
    "nvd_published_at" : null
  }
}