CVE-2026-52804: Gogs.io/gogs Gogs Vulnerable To Privilege Escalation Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-4565-r4x7-hg8j",
  "modified" : "2026-07-21T13:17:09Z",
  "published" : "2026-06-23T16:52:30Z",
  "aliases" : [ "CVE-2026-52804" ],
  "summary" : "Gogs Vulnerable to 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```",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N/E:P"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "gogs.io/gogs"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.14.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "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" : "WEB",
    "url" : "https://github.com/gogs/gogs/pull/8227"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/gogs/gogs/commit/1fdc9cc28e159135cfa4d6b11ecd5daa0f8ce22b"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/gogs/gogs"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/gogs/gogs/releases/tag/v0.14.3"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-193" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-23T16:52:30Z",
    "nvd_published_at" : "2026-06-24T21:16:56Z"
  }
}